You are shaking the dice around (whether in your hand or in a bag) and then bouncing them off a surface (either a table or the other dice in the bag) to come to rest in a particular orientation. Any bias in the dice is still relevant.

This is exactly what I'm arguing against. There is an awful lot of complete conjecture in this thread, this is what I think, this is my opinion, and so on. This is not good cryptography. The security of your private keys should be based on tried and tested methods, which are provably unbiased and are provably secure. It should not be based on guesswork and people saying "Well, I think this is probably safe enough".