Parent doesn’t talk about age restrictions on DMs and nor do I. We are talking about physical keys and only being restricted to peers that you’d know from school for online play.

I'd say TFA and thread are both talking about this. Quoting the article-

> Understanding how attractive Roblox would be to predators, the company long ago could have blocked unrestricted contact between adults and minors.

Contact here seems to be about DMs or equivalent, since I don't think grooming and kidnapping preparations are happening in public forums? So with or without involvement of a physical key-exchange, I'd say that curbing private personal contact is the crux, and it's easily doable without effecting other aspects of the game