When I first read "At Ready" in Posse Marshall info I had to ask for clarification since around our area it often means gun in hand, or hands (if stated in plural). I was informed that it was in regards to body position and hands not torching guns. I will now assume that at other matches unless there is addition to wording such as "At Ready, gun in hand or hands", or "At ready, hand or hands touching gun flat on table",
As mentioned, I also think the command is to be over-ride of SASS default. I certainly favor this in stage writing and appreciated it at EOT. TT, GAP is fun, maybe more so for us shorter folks.
IMO, if stated "in hand" then that means one hand could be on shells if stating with shotgun. If flat on table is not mentioned then I assume long gun can be to shoulder.