Because, even if you wanted the query to fail because its technically invalid, the fact that it was producing a StackOverflowError instead of a more meaningful error was still a bug. Honestly, I didn't mind which way the fix went, but it was still a bug and that's why nobody closed it as invalid :)

As a user, I'd be happy with the fix being that the variable re-use is detected and I'm given an appropriate error message (this was, after all, the fix that I deployed to work around the problem). I imagine that the StackOverflowError is not the intended "you've sent an invalid query" error. ;)

Thanks for the workaround, can confirm that the query is working again for me now :)