I'm interested to see what the uptake is among users, because even though Matrix has done a fair amount to smooth this process, verification is still a pretty large source of friction from what I can tell, and I'm not completely sure how it could be made easier. I guess the idea here is that once you verify a contact that syncs to their other devices, but in theory Matrix also does that, and in practice I still see some friction.
It's possible Apple's implementation will just be better, or that they'll rely on attestation to such a degree that they'll be able to skip some other friction points. But even with the public verification setup (which gets rid of the problem of needing to verify devices at the same time as the person you're talking to), I'm still slightly skeptical that users are going to copy and paste a code into their messaging app to verify contacts. My experience is that even popping up a button and saying, "do your friend and you see the same emoticons" is too much work for a lot of users.
Maybe I'll be wrong. And I guess ideally if iOS users get used to doing this, they might be more tolerant of doing the same thing in other messengers too.