Publishing the reason you do not support something is a stronger signal than most of the integrations you could ship. A tool in this position could quietly ask for the broad key and say nothing, and almost nobody would know a narrower one was ever possible.
The part that is easy to miss is that a decision not to build something leaves no trace in the product at all. Writing it down is the only thing that makes it visible, which quietly makes the post part of the product.
Sifat Ahmed
That's a sharper way to put it than I had in my own head, honestly. "A decision not to build something leaves no trace in the product at all" is exactly right, and it's a little unsettling once you notice it - every unscoped key request everyone else quietly makes looks identical to a scoped one from the outside, right up until something leaks.