The Anti-Santa
Learned
Checked my game in Galaxy, it apparently received the "Revision Update", that probably means you get the update to be able to install Revision? Because it is still listed as a separate product, and it even appears as a product you can "buy".
I don't have DE currently installed but in the rollback section apparently you still have the option from two years ago.
I have Deus Ex currently installed via Galaxy with GMDX installed as well. Thank god I didn't have automatic updates installed or it might have fucked things up. But if I understand what you're saying is, Revision still has to be activated and doesn't override the vanilla game when initially downloaded?