Most of the modern MA guys will still punch on the heavy bag through their old age.
Most of the TMA guys will only punch into the thin air through their old age. The following 2 clips show how Taiji guy and Baji guy punch. Please notice that both require about 1 second to "compress and release" before the power is generated.
If you put both of them in boxing ring and fight against boxer, since they won't have that 1 second power generation time, their punches will be just like the boxing punch. I believe the boxer's punch is more effective because they don't depend on that "extra power generation time".
You see the funny thing there, Chan Xiaowang openly admitted he never had a real fight in his life and was wondering if what he did ever got in a fight, if it would actually work. Also take into account that in Chen Xiaowang's day of training Chen they did have matches, that he does not consider fights. Well one day in Northern Europe, much to Chen Xiaowang's surprise, some one in the seminar decided to jump on him, he reacted and the person left in an ambulance, he felt horrible about it, but he at least knew his stuff worked.
As for the Wu vs. White crane clip, I am so tired of this thing being brought out as proof of anything. The problem you have is that there are people still alive that were there. My "Taiji" sifu was one of those people and I will. once again, repeat this...... That fight was billed much like an Ali Fraser fight, everyone was really excited, tickets were sold, many showed up. However no one, in the marital arts community at the time, could understand why the old Wu fought, they all thought the younger Wu should be fighting. But the fight happened and even the Marital artist there thought it was pathetic, My shigung and my shifu among them,. Many people in the audience were upset as well and many wanted their money back...
Can we please stop parading that pathetic show out as proof of anything now....
As for old TMA guys punching the air, obviously you have no idea about how one of my XIngyi sifu's train or how his "Old Chinese guy" sifu trained until the day he died. Also you obviously have no idea how my last Bagua shifu trained and you do not know how my Taiji sifu trained, you obviously do not know how I train and you also have no idea how my Sanda sifu trains either (but you are right he does not hit a heavy bag, he hits trees)... for that matter you don't even know how my first sifu trained or how he trained his students, and he was mostly modern Wushu and competition forms.... if you are saying things like
"Most of the TMA guys will only punch into the thin air through their old age." and before you ask... no, I will not supply you with videos from YouTube on any of this... You seem to be rather accomplished at finding those yourself.
Also you should know, or I would at least think you should know, many of this "Old TMA guys" are not big on being filmed, especially in applications. And that many today that sell videos, put little differences in these videos so that if they run into someone claiming to have been trained my them that they can tell by looking if it was in person, or by video.
Do not judge all "TMA guys" by a couple videos on Youtube