When I swam in high school, things must have been in a transitional phase in our area. This was Middle TN, early 90s. Our pool was SCM, there were a couple others, but most were SCY. The bulk had gutters, but a few were flush. No correlation that I remember between gutter and y/m. We swam in all of them in a season, just adjusting each time.
I swam back in every meet, so I started with my fleet flat on the wall in some pools and curled over the gutter at others-the governing body for high school sports in my state allowed either. I MUCH preferred using the gutter. I don't know if it actually pushed me out farther, but boy, it felt a lot more like taking flight. I think those starts were my favorite thing about competing in backstroke, to be honest.