The problem here is more with the execution of the "Legendary" trait. That its a dragon as example is a coincidence.
WotCs idea of what defines a legendary creature shows to me that, again, its all about combat. A creature is legendary because it moves outside its turn?
This dragon has no ability to affect the outside besides combat, not even skills. Its writeup suggests that it exists purely to combat the PCs. The regional effects go into the right direction but I hardly call it a step. A small shuffle at most because it is a giant rule0 with no explanation how this happens and the effects are minor at best.
The small section about the personality also isn't much when you compare the writeup of dragons in previous editions, but that is a dragon thing.
You can of course say that for a playtest they limit the examples to the relevant information and you might be right (although, then why have they published the personality entry?) but to me this example shows that with 5E WotC again has very different priorities than I have.