or tech lead. or whoever. the point is, someone has to do the sizing. I think applying an underpowered agent to a task of unknown size is about as good as getting the intern to do it.

Even EMs and TPMs are assigning people based on their previous experience, which generally boils down to "i've seen this task before and I know what's involved," "this task is small, and I know what's involved," or "this task is too big and needs to be understood better."