What no, You need to be online at least once to launch a game from Steam. If you lose connection you don’t get booted out of the game immediately.
You’re forgetting the part where if you’re not connected to the internet, did not set Steam in Offline Mode in advance, and then try to “Start in Offline” mode, it will simply refuse to do so and give you a “could not connect…” error message, as if you’re trying to connect.
This makes sense for games with a major online component like Team Fortress 2, not so for games where the only online component is leaderboards, like Jamestown and Sonic CD.
Given all these circumstances, I might as well permanently leave Steam in Offline except to buy games and play tifftwo.
this strikes me as a good idea.