Getting in to the fine details of it is important for researchers or doctors who specifically work with the tongue, but the issue that we're talking about here is how this was commonly taught as absolute fact to young children with no nuance and seemingly for no reason other than it being widely believed.

If anyone is specifically claiming that the tongue is completely uniform in taste reception then they're it taking too far, sure. But generally when I see this brought up, the focus is on questioning the process of how some facts make it in to what schools teach as "common knowledge" even when they are both wrong and unimportant to daily life and general education.

When a teacher tells a 6-7 year old that flavors can only be tasted on certain parts of your tongue, the problem isn't that they failed to call it a "spatial component to our experience of gustatory stimulus". At that age, teachers have to strip out most nuance from any lesson, and the goal is to find a way to explain things that is true enough while still being understandable to young children.

So why, if stripping out the nuance makes it basically wrong, did teachers keep teaching it for a century? Even if it were true, it's not really important information for most people. Necessarily even, because if it were important to daily life, it would be a lot easier to notice it's mostly wrong.
I don't know, and I don't think there's an exact reason. I had teachers tell us about this, then seem to realize they needed a reason for it to matter and try to turn it in to a lesson about scientific inquiry. They told us to go home and try putting flavors on the 'wrong' parts of the tongue and notice how we couldn't taste anything. I tried it once, and it didn't work, and it was never brought up again.

Feel free to educate people about the mechanics of our sense of taste, but I think this is a fine example of myths making it in to what's taught in schools.