Makes sense, there would be mass outrage if they had decided to ban all Arma 3 and DayZSA keys on steam accounts with legacy Arma 2 bans.
Going forward every time we buy a new Arma 2/3/DayZSA copy we should always do it on a new steam account to avoid losing multiple games when we get banned in one. Not a big deal. Just a PITA constantly switching steam accounts.