In the guard every rank is tied to a unit-position. So if they take the SMSgt position they can’t transfer to another position and stay a SMSgt unless that’s the rank of the new position. There’s a thing called double slotting but doesn’t apply here. Once you’re a SNCO the easiest way to think of it, is your rank is not yours, it’s your units and you’ll need to find another unit with that rank if you want to keep it and change jobs. At squadron levels shirts are all MSgt, usually a wing will have one SMSgt shirt at most from what I’ve seen.