There were a few patches to RA2 through, so the code clearly exists for a bit of time post completion.

6 total and they spanned from 2000 to 2001. Just 1 year.

That was fairly typical at the time. It wasn't uncommon for a game publisher to patch their games, it was uncommon for that patching happen too far from the initial release. After all, they wanted their game devs working on something other than the old release. The patches were strictly just a goodwill thing to make sure the game kept selling.