The Mac is a "real computer" because it can be used to create new types of software and platforms, such as the Vision Pro.
iPad is not because it cannot be used to create the Vision Pro. It may still have advantages where it's better for some uses cases, but it still doesn't make it a general purpose computing device in the same way that a TV is better for watching videos than a Macbook, but a TV is not a "real computer".
They're not great for making software. That doesn't mean they're not a decent-to-great tool for a whole bunch of productive or creative activities, often in ways that a "real computer" cannot be reasonably used as a substitute—that is, if they vanished tomorrow, in many roles they wouldn't be replaced by a laptop, but by paper, a stack of single-purpose tools, and more human running-about or time-wasting.
I think the real/not-real computer thing's not especially illuminating, but I don't take issue with it the same way I do dismissing phones and tablets as "consumption-only", a perspective I find simply baffling, because I see them used for creation and productive purposes all the time in a ton of contexts by ordinary people.
iPad is not because it cannot be used to create the Vision Pro. It may still have advantages where it's better for some uses cases, but it still doesn't make it a general purpose computing device in the same way that a TV is better for watching videos than a Macbook, but a TV is not a "real computer".