This unlocking on Steam in 22 hours at 18:00 local time is pretty annoying.
Yeah, changing release states is still one of the few things developers/publishers can't do themselves via the Steamworks Product Data frontend. It's a little ridiculous at this point. Valve may be worried about upset devs yanking access to a game by changing the state to "unavailable" (although this wouldn't affect those with a licence that has a release state override), but surely it'd be relatively trivial to prevent further release state changes once an app has been set to "released".
That all being said, games unlock on Steam at either side of the store update quite regularly (e.g.
Dog Fight released ~10 hours ago), so I don't see why Valve would say "No" to Blow wanting The Witness' unlock time moved forward.