10th Planet is an advanced system of no-gi BJJ so yes, it is recommended you have basic knowledge of BJJ and the positions of jiu jitsu. That being said, the 10th Planet instructors do a great job with new students and there is actually alot of BJJ moves taught, especially in fundamentals classes. The system is pretty diverse and some things will help you astronomically, albeit if your flexibility is shit you shouldn't be practicing rubber guard at all. You will get a thousand mixed opinions on the subject so it's really up to you to get out there and try both 10th Planet and Gracie gyms. Some people will tell you rubber guard never works, and it's all wasted time when you could be working the basics. Well, Vinny Magalhaes has something to say about that. Another thing to consider is price ; I would say 10thPjj charges less than your average BJJ school.
Good luck in finding what suits you best.