I know it's a joke, but those graphs are wrong, as is the way we talk about learning curves.

If something has a steep learning curve, it's easy to learn to use. Look at the vi graph: Assuming the x axis is time and the y axis is knowledge, according to its chart you know how to use virtually all of vi as soon as you start using it.

Things that are hard to learn have shallow learning curves: it takes a long time to become proficient.

I think the x axis should be rather interpreted as "learning progress" instead of absolute time - then it makes more sense.

But ofcourse when read like that it lacks the absolute time reference (notepad can be learned in a day whereas vi takes months) and generally yes, this is just a tongue-in-cheek sketch. - Still, not too far from reality, imo.

Thank you for saying this. I correct folks all the time on this and while they agree steep == easy && shallow == hard is correct, it's 'counter-intuitive' (their words, not mine).

vi is easy, you only need to know ~5 commands to be useful in it.

No, a learning curve has incremental knowledge on the X-axis and effort on the Y-axis. The more effort you have to put in to learn that next important feature makes the curve steeper. This is also why learning curves typically level off at some point.