That's just the problem: that if it's not physically verifiable, it's not knowledge. That's what I disagree with.
Suppose everyone in the universe were blind, and there were one man who could see. He couldn't prove his sight to anyone else. But would his sight not be "knowledge"?
We are all in that position in our own little universes of personal consciousness -- we are all blind to everyone else's inner world and have our eyes open to our own (hopefully). We can try imperfectly to talk about our own experience and hope some of it gets across, but ultimately we know that language is limited even at the best of times...
The blind man's sight can be empirically tested. He can say, "there is a rock four paces in front of you half again as tall as you are."
The person he is talking to can then step forward four paces and feel if the rock is there, and if so how tall it is.
In the case of external repeatable phenomena, science can be brought to bear.
Internal (that is mental) phenomena are not its province because they cannot be independently observed.
Internal phenomena can be discussed, accepted, rejected, practices taught and so on. I can say that I know Tai Chi has helped me with a great deal of self control, but I can't prove it to anyone's satisfaction. I can suggest it on grounds of personal testimony and somebody else can try it and find that it is or is not useful to them.
But I can't and don't say that its utility for me proves the underlying chi theory (it doesn't and I don't). Nor do I think Taoism accurately describes the universe even though I get a lot of utility out of its teachings.
So what knoweldge do I have from this. The knowledge that a particular set of disciplines are useful to me. That knowledge I can share and others can accept or not.