I think in Su's five elements you can see him very gently tightening his fists and then relaxing them again. I have never met Su Dong Chen but to my eyes the key components of timing, posture, tension, relaxation, rising, drilling, falling and overturning are there in his Xingyi. I assumed watching him that there was some reason why he didn't want to display the Fajing overtly.
The same components are present in
Feng Zhengbao's Xingyi. However, Feng's intention in this particular instance is not pedagogical as Su Dong Chen's clearly was but to display Xingyi's true power. This is great if you know what you're looking at but if you have no idea you would miss a lot you would just see Feng moving rapidly without being able to understand how he's generating his power.
It comes down to the intention of the two masters in the two different instances. I'm sure if Feng were your teacher he would slow down and show you exactly at what stage he was wrapping, coiling, how it related to his breathing, the turning of his wrists, forearm etc.etc. Likewise I'm sure if Su was seriously fighting someone he would be showing all the elements of Fajing that he and his Kung fu brothers such as Xu Hongji and
Luo Dexiu gained rewown for.