HereForTheBeer: Just for grins, try this test to see what happens. You'll still have your Steam account just in case it all goes to hell (it won't, but still):
Set your Steam profile to Private, or whatever setting is the opposite of Public.
At that point, gOg will no longer be able to see if you still have title XYZ in your Steam library that you then got here through Connect. Wait a couple months and take a look at your gOg library to see if the game is still there. If they are periodically scanning members' accounts to make sure they still have the Connect-ed titles, then maybe they will disappear from your library.
To be even more thorough with a test, request that Steam Support change your username. You'll still have the Steam account and your games, but gOg won't recognize it as as existing account since they'll only know to keep searching the original account name that you gave them previously. If your games disappear from your gOg library, then report back to us that they do indeed remove games as mentioned in your concerns.
I REALLY don't think gOg is that concerned about the ongoing contents of your Steam account library. DRM-free is built on trust, and I think that once the initial verification happens and your game gets Connect-ed, then there's no more concern from gOg to make sure that title remains in your account, or that your account is still extant. That would go against the spirit of DRM-free, and I don't think they would gain anything but bad publicity by making that move.
Good ways of testing indeed :) But I'm waiting for a new answer from the Support team, maybe they can permanently solve this dilemma this time, so I'll wait for that first. I'll report back whatever that's gonna be.