Do you by any chance have Judi Madson's (Green Fairy) book "Quilting Wide Open Spaces" I think she addresses this very issue. Unfortunately, I don't have the book handy to paraphrase for you. There are two schools of thought on the issue. Leah Day (who quilts on a DSM) is an advocate for open seams. Here is a link to a blog posting of it
http://freemotionquilting.blogspot.c...ing-seams.html
I don't necessarily agree with Leah. I think I am in Green Fairy's camp of do not press your seams open.
I am assuming you posted this question because you have a client quilt and they want SITD and they pressed the seams open. If the client did this and wants SITD then give them what they want.