Ahhh - that's exactly what I did last time (for my PR app) and that's also exactly what happened (CBSA came thru before IRCC).
But right now I have a different, unrelated PA request with CBSA - I've never tried to have multiple outstanding PA requests before with the same agency. Now, it seems like this shouldn't be an issue (if they look like they're for unrelated things - which they are - they'll just be assigned to two different people and handled in order; worst case, if they look like the same request, they could get merged or at least handled by the same staff worker, not a big deal) - but do let me know if I'm missing something.