I agree with your first point in the sense that having individualised targeting data necessarily improves advertising by some amount vs. merely contextual and aggregate data. For our specific case I'm not convinced that amount is as big as some people imagine it is, but I haven't found a good way to test that precisely given that facebook doesn't really have a "just give me a representative sample of your audience in this region" targeting feature (wish it did) to compare with the targeted alternatives. In our case, app ads that now use SKAN (the Apple solution that provides aggregated attribution) seem to be working well enough - that was my point.

Regarding your second point, yes, I agree - it's not obvious. Assuming this did indeed affect many developers like us and that it happened to everyone at the same time (which may not be the case - that it happened to us and that it coincided with their earnings report may have just been a coincidence - I haven't seen a mass outcry on twitter or anything), I was wondering whether it might be hedge funds that buy/track aggregated ad spend or attribution data, perhaps from MMPs or media buying agencies. I know they buy app download data from the likes of App Annie, but don't know if equivalent data is available and timely for ad spend. In any case, my point is more that this is illustrative of how they make bad situations worse for themselves.