I don't see how this is a question. GSP had some holes in his game, so he did what any good fighter does and addressed them, and became a better wrestler and BJJ guy.
Any good fighter also analyzes their opponents and takes the fight to where their opponent is weak and they are strong.
Thats what GSP does. Serra, or not wanting to strike have nothing to do with it. For instance if GSP does end up fighting Shields, you can be sure you will see him keep it standing, because he knows his advantage standing is bigger than his advantage on the ground. He might even do it with Kos, but I doubt it.
If you want to win, you use the biggest advantage you have, and for GSP, its wrestling and top control, so he would have to be an idiot not to use it.
edit - as for Miller, I agree if your point is he should be in the UFC, I always wondered why he wasn't, he is a reasonably well rounded fighter with a big personality.