I love the quote. I do not think cycling at the top level (or many other sports) is healthier than not doing the sport. We've all see the retired sports pros in their 50s.

Your assessment in the 2nd section is correct, but you can have imbalance without injury. Especially in the legs being significantly stronger. If the rest of the body can't take the strain in a squat that the legs can deliver - don't do squats. That bothers a lot of people to say that.

The stretching is also something I don't see needed to avoid weigh lifting injury, or needed for cycling. I don't agree Yoga will do what heavy weights on a leg press will do for peaking the power meter.

In many crashes where the limber rider may fare better, but that again brings us to the earlier topic. It is better for total health, but maybe not for going faster.