No, there's more to take from it then just 50 post. People would be padding their post like crazy if that was just the only rule.
What's also taken into account is actual time here. You've been here less then a month and the community needs time to get to know you.
Lastly, and one of the teen specific mods or another mod can say differently, but you are the older side of the teen area. Most of them entering the teen section are 14-17. 18 and above from new members are generally considered already aged out as their teen years are pretty much done, like when you turn 20 in less then a year.
The teen section is pretty much invite-only, and those invitations are not given by any strict metric of time or post count. They all factor in, of course, but at the end of the day, what matters is the impression that people here know what kind of person someone is. If you just spend all the time lurking and telling very little about yourself, that is going to take a lot longer than if the topics you post in are those that reveal what makes you tick.
Now if all the middle age ppl would just go gracefully to more age appropriate websites this would truly be a youth forum again.
Our target age range is 14-40. Yeah, 40 is a bit high for a youth community, but many INF-affiliated organizations have their youth range go well into someone's mid- or late 30s, so the people here are still young by naturist standards.