I don't know. You are right but experiments show this behaviour.
Many times I read BOL or some other documentation I feel like being in the helicopter.
BoL often makes me feel like that. And the experiment in this case shows another oddity: when in autocommit mode, a reference to @@tc in the statement bring auto-committed will be evaluated before the transaction is started (hence the 0 count in the first and fourth rows).
I've written quite a lot of things that look at @@tc for various reasons, but results like these make me very very careful about doing it!