I remember seeing a video several years ago (link shared by someone on this Board, as I recall) that debunked several quilting "truisms." Actually, he said that while they might be true for hand-quilting, they did not apply to machine piecing/quilting.
If memory serves, the speaker said the following:
1. It's ok to press seams open.
2. It's ok to use poly/cotton thread.
As a result, I usually press my seams open, and it works very well. And I always use poly/cotton thread. No problems so far.