Wow, this is sad. I honestly thought AC had more class. He had to have known pretty quickly that Andy had a problem, yet he attacked hard through the rest of the climb. It seems very clear that he chose to capitalize on Andy's mechanical. Classless.
And yes, there's a huge difference between this situation and the stage 3 situation when AS gained a little time. Riders were falling and having mechanicals all over the place in that stage. It would be completely impractical to wait for certain opponents who got into difficulty. Plus the top riders had yet to emerge so early in the race, so how would a rider even know who he should wait for? No, the only thing that would have any chance of working would be what they did in stage 2 where the whole peloton agreed not race at the end.