What worked for me: Sign out of your main apple account at the top of settings, do not log in there with any account. In the developer settings, stay signed in to your sandbox account (I was also signed into game center with the same sandbox account, I don't know if that matters). In developer, tap on your sandbox account, manage, set your age range that you want to test. Now don't use test flight, play the app directly from xcode onto your connected device. This gave me the correct behavior. Then close ther app, change the age, open the app

update: my update was reviewed this morning, after 10 days

My update finally got reviewed this morning, took about 10 days, in the past updates were only about 1.5 days

it's happening to me too, it looks like it's happening to everyone right now. Massive backlog caused by ai generated apps