Facebook owns Whatsapp, and Instagram and a bunch of smaller stuff as well. But Meta is just not a great brand. It's a vague ambition at best. That's the problem with this rebranding. Google did it because they had a bunch of aimless acquisitions/spinoffs, none of which since managed to rival it's money maker Google, which continues to be the place that is associated with their successful stuff (Android, Youtube, ads, etc.).
Facebook is doing it because their Facebook brand is imploding due to years of mismanagement. It's a dead zone at this pont. I check in once a month and then leave in disgust. Absolutely nothing going on there whatsoever.
Square on the other hand is a successful product. Nice growth. Nice brand. Worth going all in on. The stuff they acquired pales in comparison. Why mess with that brand, create confusion and awkwardness, etc.?