Like earlier, a chat administrator who doesn’t have permission can still send a private invitation through an individual chat. The request will disappear after three days, so you can ignore it if you’d rather not respond.
The feature should be active now on Android and iOS. This is an acknowledgment that unwanted group invitations are still an issue, of course, but it’s also part of an ongoing effort to fight fake news. There should be fewer opportunities for people to spread misinformation, at least to people who weren’t already receptive to it.