The title pretty much says it all. Do you only test for pinning when you are shot at with surpressing fire? I've been playing since april fairly regularly, and not once has anyone used Surpressing Fire, and therefore, pinning has yet to come into play at all.

Am I missing something important?

That is the case. Full Auto Fire, as I understand it, is concentrated on a single target or small area. Suppressing Fire, however, fills the air of a sizable area with lead/las-bolts/etc, forcing people to get into cover. It's not accurate shooting, but the primitive part of your brain doesn't know that - there's shots everywhere and standing out in the open is really dumb.