I give you Google, the app:
https://apps.apple.com/us/app/google/id284815942
Google search, in an iOS app. Not everyone uses it, sure, but has over 341k reviews. Facebook, as a point of comparison, only has about 4x more reviews at 1.2M. 4x is a lot, but it's also a lot less than I'd expect over something primarily used in the browser.
If what FB is saying is true then the move by Apple helps Google. There's more or less two options for online advertising. So if companies spend less on FB then they're probably going to spend those dollars with Google