I'm actually not a native speaker, so indeed, I might not know. I checked in the dictionary though. This is an analogy, but not a very good analogy, because of the reasons that I pointed out. Are you disagreeing with any particular reasoning there? Or should I just say "they're similary, but"?
An analogy does not require that the items involved actually be similar, only that the relationships in each are the same. For example, "Gasoline is to cars, as sunlight is to trees" is a perfectly good analogy, even though gasoline is nothing like sunlight, and cars are nothing like trees.
In much the same way, comparing "Apple writing a C interpreter on top of llvm" to "Alex Gaynor writing a Ruby interpreter on top of RPython" makes a very good analogy, even though Apple is not much like Alex Gaynor, Ruby is not much like C, and PyPy is not much like LLVM.
A good explanation, and further, many times a good analogy relies on the things being very different in every way except for the one way it intends to emphasize. An analogy is often a way of saying: "Let's focus on this (often very abstract) aspect of interesting similarities. Yes, you can easily point out many other dissimilarities. That ease means I'm not talking about those aspects, so if we understand each other those don't even have to be mentioned."
"They're similar, but" is much better than "is totally not like." The point of the analogy is to give a high-level view, not to achieve 100% accuracy at the lowest levels of detail.
You're right that the analogy doesn't quite capture everything here. On the other hand the analogy gets across most of the point.
I would have said "That's mostly right, but the interesting thing about sharing code on a VM is access to VM features and code shared on the platform, not just that it's possible to decouple a front end from a VM."
