This is definitely apart of the game. I will have to look at this more closely when I have time as you will always find yourself in this position. My Instructor works this quite a bit and can move most people off him when he is on the bottom by using his legs to manuever you off-balance. Also work on when you are on top and releasing your leg from the half guard like the mountain. Probably another term for this but we call it the mountain where your knee looks likea mountain and you work your opponent's leg down it and then out.
"IF I COME ... I'M BRINGING THE PAIN WITH ME"