Even Time-Stop is an AV genre in Japan. Though the actresses tend to be those that are beyond their prime. It's the sad lifecycle of AV really. The ones that fall off as they age tend to take up more and more out-there content so that they at least still have a job.
Age has nothing to do with anything. It's about success and catching the audience. JAV actresses are like idols. If you cannot attract viewers and gain a fanbase, you'll end up doing low-tier jobs. Lots of old JAV actresses are very successful even after thirty. The main issue here is that JAV is filled to the brim with many actresses so it's hard to make a name for yourself. I remember once seeing an AV where the girl had to visit India and do nudeshoots in public. The entire video is just too uncomfortable for a normal human being to enjoy. I'd say it's dumb on the girls' part as well because unless you're literally on the verge of dying from starvation, you should never agree to that shit. But yeah, the girl was not that big of a deal which is why she was probably approached with this offer and she accepted it as well.
Just like how when idols don't end up being that popular, they will go work as a hostess or do gravure.