I’ve found another thread of a guy having the same issue (Multiple Instance: How to obtain LoopCounter in External tasks?). Linking it here since he worded his thread is way fewer words.
I am not going to revive that thread (as its from `19), but that shows this issue hasn’t affected just me.
Is there really nothing to be done? I am willing to accept “janky” solutions if that is the case, using User Tasks for my use case would bring way more complications than whatnot.