While there is a subjective difference between 'pain' and 'soreness' both tell you that you somehow exceeded your bodies capacity, and both are warning signs that tell you to do something differently.
Without seeing what happens on either side of still images it's impossible tell exactly what is happening with Pedro's followthrough. The fact that he seems to finish 'lower' certainly seems to indicate that something is different. I'm aware that he missed most of the 2001 season with a rotator cuff injury, but I don't know the specifics. It would be interesting to compare mechanical differences from before and after this injury. I also know that he has had hip problems associated with pitching.
For as long as I've been around ball (over 40 years) I have always heard people say that, "Overhand throwing is an unnatural act." So much so that I accepted it as gospel. Based on what I have learned over that last three years I think this statement is untrue.
What would you think of someone who can pitch with serious intensity every single day, seven days per week, for over two years without structural pain? I just returned from seeing my son in Florida, and this is exactly what he has done (and continues to do). After throwing 184 maximum intensity pitches in the space of two hours, on one day during a research session, I saw him throw in a college tryout the next day, topping at 86-87 mph. And all of this after throwing ten straight days of 72 pitch bullpens (maximum intensity). When he comes out of his current training regression he will throw even harder (and his velocities already exceed those of when he was drafted in 2003).
He has spent the last two years learning a completely different throwing mechanic. His arm drives quite close to straight forward, and decelerates pointing very close to straight at home plate. So, do I think that high intensity baseball pitching is a health hazard? No...only if we keep throwing the way we currently see it done.
I will be happy to write more about this if you care to read. Send me your e-mail address and I'll send you a clip of something different.