My pup is currently 9.5 months old, he has the wobbly hips at times, gets tired fast, likes to be helped into car onto bed etc. But I honestly just think he enjoys being helped up and the attention, lol, and probably a bit lazy. He does do the frog sit, but he has done that his whole life, and he does a normal sit at times too, just depends. He also likes to lay down and eat, but he has done that since we got him at 3 months.
I take him swimming and all of a sudden he can go for hours, running around the shore like a crazed animal. I think he is just a more relaxed pup, yours perhaps is very similar.
I think you are just worrying too much, I think unless he is doing bunny hop up stairways, then you should be concerned.