Hi Derek,
We have a similar requirement. We use Survey123 with Collector for field support or situation awareness. The challenge is that we use Inbox assignments only. So we want the field inspector to see their own assigned work, and only their work, on the Collector map. Sure, we could set up a filtered feature service layer for every single one of the 40+ field team. But that's cumbersome. It would be nice to mirror the Inbox filter on S123 forms, such that the logged in user sees what is queried to them by UserID. I think that's the unmet need -- for me, at least.
Please let me know if I'm missing some kind of dynamic filter on the feature service layer? If that works by user ID in Collector, then bingo.