“To practice the method of Bagua Boxing, first find a knowledgeable teacher to instruct you who knows the meaning within the boxing art and the order of the sequence.“
Read it carefully and let this sink in for a moment. What is clearly indicated here is that there are other Bagua teachers. Cheng doesn’t say anything about that only a few taught the art, or that it would be hard to find a Bagua teacher. He says it in the way like it was possible to pick and choose amongst teachers. So from this statement, I can only presume that there must have been other Bagua teachers around except the few well known students of Dong Haichuan.
Reminds me of an old joke:
Q - How do you make a small fortune in the restaurant business?
A - Start with a large fortune! (cue laugh track)
From this joke, we can clearly see that there are many people around with large fortunes willing to invest in restaurants. Thus, I can only conclude that bagua's circular footwork was devised as a method for waiters to move between and around tables.
I'm just making jokes, here, but there is quite a bit of sketchy logic in that article.