Yeah fs and bs refer to which part of you is facing what you're about to grind. So your body turns frontside for a backside boardslide. But you turn frontside for a frontside lipslide.
My whole point wasn't necessarily stuck on the fs/bs stance, it was that no one's ever done a frontside "nosegrind" straight on a rail. So the term "overcrook" is implied backside, just like a Suski grind.