I go to my knees and turtle up to escape side control regularly. In fact, it's my top way out of bad positions. And Brent gave me a couple of crucial details in a private lesson that have made my movements exponentially better and more efficient. Any time you can spend with with him will be worth much more than he charges you.
Regarding Telles' style, it is very dependent on Gi grips and he even says in his set that it's more of a position for the Gi game. He is comfortable hanging out in those positions, and it appears that feels that way because he can control and manipulate his opponents hand positioning via the sleeves grips.
In my experience (which is to be taken with a grain of salt, I suppose) turtle is great for no Gi, but it needs to be more of a guard repositioning strategy. If you hang out there you can start getting in trouble. There are a couple of guys in my gym that will snap on Japanese Neckties/darces from there and one that will jump into the truck during transition. You gotta be wise to what your opponent is capable of. Of course, if you make any mistakes with your elbow positioning or your knees there is opportunity for your opponent to get a hook in, as well.
The turtle idea that I use most often is actually something I picked up from Saulo Ribeiro's DVD. He calls it "The Running Man Escape." It's a guard recomposition that he uses. Excellent stuff and very high percentage for me. Usually lands me in guard with an arm trapped to the mat.