Because that's how various tools find the symbols file. The UUID is unique for each build and symbol file and is indexed by Spotlight. Symbolification also depends on Spotlight indexing the symbols file. That's the explanation for @grzywacz's post.

expr seems to work

@FrameworksEngineer I filed FB8768071. In my case I have a bad interaction between UITableView and the NSAttributedString() init method that converts html to an attributedString. It was being called while updating a tableViewCell and this caused cellForRowAt to be called again while my app code was already processing a cellForRowAt call. And the tableView lost its mind after that.