The continuing series of qualifications "it's kinda like this, for what you're talking about" gets pretty rough there, even when explaining, say, Kubernetes to adults! It can be a confidence crusher.
There's also the flip side response which is always asking a lot of questions about "well then what are the other sorts of numbers" and eventually getting shut down "we're not talking about that now" which comes back to the "who decides what you're smart enough to hear about now" question in its own way. Or "oh the teacher doesn't actually know what the difference is, or why this isn't 'true' 100%."
Despite the cutesy name, I don't think omission of detail is the same as lying. It's often impossible to tell 100% the truth. You probably don't even know it yourself!
If confidence gets priority over truth in explanations, then society will churn out people who are confidently wrong. This is a bad idea even if everybody does that and even if it is the traditional approach.
If people were honest that they don't know something then the world at large would be a lot nicer to live in.
I think this is backwards. The public at large are pretty honest that they don't know math. The world would be a much better place if they were able to do practical algebra, even if the higher truths of abstract mathematics never enter their minds.
I really don't see people being confidently wrong about abstract mathematics as an issue. I certainly don't know the rigorous definitions of an integral, but I can apply the concepts of calculus to everyday life perfectly fine. People who care about rigorous math can do rigorous math, and I'm glad if they teach me an intuitive understanding that lets me live a happy, productive life.
Personally, I find layers of abstraction necessary for learning. Maybe there are people who don't, I suspect they would have to be prodigies though. Tell me how to add fractions practically, then teach me the principles when I need to know them. Framing that as a lie seems wrong to me, I'd call it "bounded knowledge".
It seems to me that the way to build people's confidence in their ability to learn is to allow them to learn. That means not making oversimplified statements because you don't think they're "ready" for more details. It means giving them the details, and letting them decide when they've had enough for now. (Of course one's time, say in a classroom, will be limited, so at some point one has to say "we don't have time to go into this further in class now"--but that's still letting them know that there are more details, and they can dig into them further on their own.)
That doesn’t work for lots of people (including myself). If you’re spending a lot of time on details that don’t actually matter for the topic at hand, it takes away mental bandwidth that should be spent on the topic being covered.
Refusing to answer curious students questions isn't helpful. Giving them a hint and telling them you'll get back to it works fine. They're smart enough to understand they aren't having to wait because they're incapable of understanding, but because other things need teaching first. I know I did. The good teachers were encouraging of the curiosity while back-burnering something, others responded less patiently with things like "we're not there yet!", which made them seem like bad teachers to me, even back to elementary.
> The continuing series of qualifications "it's kinda like this, for what you're talking about" gets pretty rough there
The qualifications are there; that's just a fact. Being told about them, or at least about their existence if not every detail of them, up front seems better to me than finding out about them later on when your mental model is solidified around the simplified version that you then find out doesn't always work.
> I don't think omission of detail is the same as lying.
Saying "multiplication is repeated addition", without qualification and without any caveats, is not "omission of detail". It's a false, categorical statement, i.e., lying.
As for where the line is where you stop giving details, obviously that will depend on the circumstances. A teacher who says "we don't have time to talk about that during class today, but yes, there is much more detail here that you can look into on your own" is not lying and is not saying the child is "not smart enough" to take in all the detail now. (Bonus points if the teacher says "see me after class and I'll give you some pointers on where to go for more information".) A parent who says something similar because they have to get dinner ready and the child needs to do the rest of their homework before bed is also not lying and not saying the child is "not smart enough". Limitations of time are a fact of life, and children need to deal with it just like the rest of us.
A teacher who just says "we're not talking about that", or who doesn't even know about the qualifications, or who gets snippy when a child asks a natural question, is obviously not doing the child any good; but that is because of the teacher fixating on a simplified model and treating it as "the Truth", so doing more of that won't fix it.
There's also the flip side response which is always asking a lot of questions about "well then what are the other sorts of numbers" and eventually getting shut down "we're not talking about that now" which comes back to the "who decides what you're smart enough to hear about now" question in its own way. Or "oh the teacher doesn't actually know what the difference is, or why this isn't 'true' 100%."
Despite the cutesy name, I don't think omission of detail is the same as lying. It's often impossible to tell 100% the truth. You probably don't even know it yourself!