If a game adds or changes content outside of extra add-ons like DLC (such as a free update) does that content have to be reviewed by ratings boards and risk changing the rating of the game?
I was talking about bg3 and how a certain part could be changed to be much darker, and it occurred to me that it possibly could affect the rating of the game if they did (being vague purposely to avoid spoilers). But then I wondered "do things like that even have to be reviewed by the rating boards?" Because Larian has made a lot of changes like that to the game and I imagine it would be pretty ludicrous to have each and every one be reviewed to see if it fits within the current ESRB and PEGI ratings of the game.
generally the raters aren't actually rating the full game anyhow. (they play for upwards of four hours.)
also, during development, the devs are supposed to send the worst bits on for review and rating (including package of other bits and pieces.) and the rely on hefty fines if something is found that exceeds the rating they were given.
the ERSB supposedly flags games with updated content for review.
Many (most?) ratings these days are self-assessed by the developer/publisher.
The review process has been heavily streamlined through IARC, so you can effectively get ESRB/PEGI/etc simultaneously. Governmental ratings (like GRAC in South Korea) still require you go through the government agency -- but some stores like Epic or Oculus can effectively do this for you -- and even then it's still self-assessed.
Some of the storefronts offer help with ratings, in a way doing what a publisher would do, if you self-publish. You take a quiz to determine ratings and ask questions before the rating boards even know you exist.
Ratings boards don't typically play the game. Sample screenshots and descriptions can be included in some submissions, especially if there's a grey area or the submitter is inexperienced, but it's often just apply and get your cert.