Hmm in all the garment sewing i did I never had my seams (which were pressed) open come apart. Think about it. It is the line of sewing ehich keeps a seam together.
Do what you like in quilting but din't be afraid to press your seams open because it might fall apart.
I like to pressopen. Seams lie flatter and I don't have to worry about which side I ' m supposed to press to. also avoids the humps ehen side prssed seam gets twisted!