I think these need to be split out.
TCC definitely does not come from Wing Chun, but Wing Chun definitely uses Tai Chi concepts.
This is why I initially asked if they meant "Taiji" in terms of the concept of Yin/Yang - since that's quite common. If Wing Chun uses the concept of Yin/Yang interplay, that is far more believable.
Going back to Internal and External:
I think words like Internal and External may have influenced Taijiquan for the worse.
For example, when people call Taijiquan "Internal", many people think that it's "less External" than "External" martial arts.
A lot of performative Taijiquan are very wishy-washy, flowy, flowery, and blurry. Many will claim to have structure, but donât have any details or prescriptions on what defines a good structure in the art.
From speaking to some of them online, I have learned that many of them believe that the physical shape/angles of your body arenât important to having a good structure. They believe that angles and shapes do not matter, and their justification is that itâs all âInternalâ and youâre not supposed to see it.
As a practitioner of Taijiquan, I disagree with this. Just like Wing Chun, I also care about centerline albeit it might be in a different context and usage; that term is used in my lineage. And in lots of Taijiquan videos and from playing Push Hands with outsiders, they donât care about centerline at all. Theyâre incredibly vulnerable.
Thereâs a practitioner who has told me that Taijiquan does not follow Newtonian Physics because itâs âInternalâ.
Itâs quite ironic to name a martial art after Taiji because one would think that they would advocate for both Internal (Yin) and External (Yang) among other things.
One could say that every martial art is both Internal and External; it's just a matter of ratio. There's no martial art that's absolutely just one and not the other.