To add to what derExperte said, the store region option works as follows: you're given up to two choices, one based on your current IP and another based on the region within which you last completed a purchase. If the two are one and the same (e.g. you have US IP and you last purchased something in the US), then obviously you'll only see the one choice.
Well, say, Russian users can still play their new games outside of Eastern Europe unless the sub itself has a runtime-level restriction (e.g. Black Flag). Valve's changes to cross-region trading apply only to gift copies, but they don't apply to users within that same region -- e.g. a Russian user could gift a fellow Russian a copy of, say, FF Type-0 HD which could be activated without a runtime-level restriction because no cross-region trading took place.
That all being said, Valve implementing the new store region system earlier in the year had what, at this point, I can only assume is a known side-effect of breaking pre-existing runtime-level restrictions as I can still install Duck Dynasty without the aid of a VPN even though the sub is set up to disallow Australian IPs from the running the game and it most definitely would not install before.
