I see SIWE being pushed hard. It's like "hey Meta, you spent time trying to correlate all my identity to build an accurate profile? Let me make it easier for you by using the same identity on every app".
IMHO having a “universal” profile and having a “single” profile are orthogonal. I still want to have more than one profile (e.g., one for serious discussions under my name, one for anonymous shitposts, etc); but I’d also like these profiles to work and be portable across platforms.