How can he claim to work in the industry for over a decade and not know how it works. Don't worry I know, that's why I didn't put a question mark?
Going gold means the game
is complete. Literally, it's a first party requirement. Once it goes gold manufacturers burn green discs, which are silver, then send them to the studio for retail testing. You have to test on retail hardware but that can only be done once the game is final. Going gold means the game can be completed, all items are unlockable and all achievements can be unlocked. It's complete. It has to be because if people don't have the Internet they can't download a day 1 patch to make it playable. The devs, mostly, say that in their statement.
It's really a first party thing as there's no governing body for PC compliance. Steam verify the installer package is valid but barely test anything. Just because the game is complete, that doesn't mean it "works". First party have many insane and a few sane requirements. Stuff like... the game can't crash more than 3 times (5?) in an hour. Insanity! If the wording on a message reads (I hate compliance) something like "Playstation" instead of "PlayStation" or "control pad" instead of "controller", that can be in the day 1 but likely a must-fix before. They always ask for a 100% unlocked save file to be included on submissions too. That's so they can check all the unlocks without unlocking them, therefore they never really validate the process which... whatever.
First party have a points system where you'll fail if you get too many. Re-submissions used to cost ~$50,000 but they brought that cost down like over 10 years ago. That's why games used to work on day 1!
"Going gold" isn't a PR move, like Donkeytron states. It's a milsetone which means the publisher will give dev their money (unless self publishing). They don't get much so be happy for them. Reading between the lines; going gold while announcing a delay means something hit the fan. Probably all performance fixes? You do have a set window for submissions, so maybe they had to hit a specific date but wanted to polish the game more? I've always been very sceptical of it. To me teh game looks like a boring cross between Fallout and GTA, with no longevity. Meh. They've thrown so much money at the project, it has to win game of the year and be number 1 on each platform or the studio is shuttered.
...it will sell in record numbers because people have been brainwashed to like it for nearly 8 years! People do as they're told. It might also be a genuinely good game? It's the most anticipated one of the year and releasing in the holiday season with a new console generation. Worst case, they break even.
We all know they delayed it just for do over DSP. Now the day 1 begnations won't clear early enough for him to buy Khet <horse insult>.