I've come across an article by Gunther Weil, who historically has a prominent background/position in Mantak Chia's teaching.
Weil argues for questioning the value of that teaching -- and all "progressive" Neigong teachings. He advocates instead for "effortless effort" such as that in, for example, the "Zhan Zhuang" perspective.
In some respects, it sounds like a Dzogchen kind of non-duality, non-practice "practice" in which Wu Chi has the same status as Dzogchen.
I've come across similar people before . . . and I notice 2 things.
First, if the person gives me the impression that he knows from personal experience what he is talking about in advocating against "progressive" spiritual practices . . . I can't help but notice that he's usually done A LOT of those practices at a deep level before coming to that conclusion.
And second, if the person gives me the impression that he DOESN'T know what he is talking about . . . he's usually NOT done those practices at a deep level.
The conclusion I myself draw from that . . . seems a pretty obvious one.