The Zwift ride I did this past Tuesday and synced to Connect recorded intensity minutes as it usually does even though I don't record it as a workout.
I've done a couple of Zwift rides since but it's no longer showing the intensity minutes now like it has in the past. Connect shows the ride and the ride data but not as the intensity minutes anymore. I've changed nothing in the setup and never needed to record it as a workout in Garmin for that to work.