The fact that a martial art technique is a guess invented right now to explain the origin of some Tai Chi movement does not mean that it is a bad technique.

If the one who made the guess is competent, it may be an excellent technique. However, the fact that it is a good technique does not mean that the guess is right.

The problem is that there have been far too many examples of martial arts experts, especially among those from Asian countries, who instead of saying that they have invented some techniques themselves, or at least that they have altered them significantly in comparison with what they had learned, they claimed that they had learned them from some older master exactly in the form that they demonstrate, and that the older master had in turn learned them exactly in the same form from even more ancient masters.

So when someone claims that some technique has been transmitted from their masters through several generations, that is more likely to be BS than truth. In Japan there are better sources of historical evidence, because the martial arts were practiced by professionals and there is a lot of written evidence from their training schools, but in China the martial arts that used non-military weapons or no weapons were more likely to be practiced by outlaws, with few exceptions like the bodyguards of various VIPs, including the emperor, so the written evidence is more scarce.

Unlike these claims of false antiquity, which I strongly dislike, there are also many attempts done nowadays to reconstruct the original movements of the forms of Tai Chi and of other Chinese, Okinawan etc. martial arts, which are presented as what they really are, i.e. guesses.

Those attempts of reconstruction, carefully done based on various lines of evidence, which are presented openly, are very interesting and I enjoy them very much.

If there still exist people who have preserved non-public details about how Tai Chi really was 200 years ago, they are likely to be found in Taiwan, because in mainland China after WWII there was a period of oppression of all former martial art experts, so few masters of Tai Chi or of other arts have survived through it, therefore most of the knowledge that has been preserved was that of the beginners, who according to tradition were not taught the complete art.