> Another theory: that for some people, hitting a problem is an excuse to stop working entirely and claim to be waiting on another team for support.

Agree, but sometimes it isn't even the user's fault and they do things like this out of desperation or frustration.

Imagine working in a place where nothing works right, you always have to search through shit documentation to find tiny nuggets of wisdom, and everyone is always pushing to get more done in less time. Then, if you sense a chance to have a short break by throwing something over the wall to another team, you might also choose to do that rather than work even harder to try and find some missing answers for the questions you seek.