I just saw the countdown change as well as the date? What's going on? Is this simply the time the pre-load unlocks or has something changed because of the retail leaks? Would appreciate some clarification.

Noticed that too.
It's just now correctly counting down to the pre-load going live, in a little more than 11 hours.

That's most likely the date for the preload. GOG was said to load it 2 days before launch.

Thanks guys, didn't want to get overexcited for no reason lol.

Although I just noticed that it's technically a bit of false advertising claiming that "this game will be available for full download on Dec 7, 2020".

why do you say it's false advetising ? the game is supposed to be available for pre download on GoG today, still playable only on the 10th

It will still be missing the main executable, or something similarly crucial to the game actually becoming playable.
So, technically not the full download.

It's all good though, I was just trying too hard with my little jest here...