In one of the newsletters Admin discussed this. He said that in the garment industry the seat seams have always been pressed open and look at all the stress put on those seams.
Actually, high-stress garment seams are usually flat-felled or triple-stitched, others are serged, top stitched through seam allowances... even dressmakers at home, sewing for their personal use, generally finish seams for their function. I would never make a sleeve or center back/crotch seam on pants, for example, with just one line of sewing and then press it open! I might do it on a shoulder seam, with the collar seam at one end and the sleeve seam on the other.