The "scholar" is selling himself off as an "expert" in the matter of Z visas and gives wrong advice.

The 'scholar' is not " is selling himself off as an "expert" in anything as you claim, but merely offered advice to a person asking for it. Where do you see the words 'I am an expert' in any post of mine ?
The advice given in good faith to Bob was accurate and based upon on personal experience, so despite claims to the contrary from those not even in China or dealing with various PSB's over visa and RP matters, my comments on the situation for someone wishing to come here and teach are, in my opinion, worthwhile.
Any amount of bleating from certain quarters who are plainly miffed that there is some other who is in a better position to reply to a request for information will not change that. Of course anyone may take or disregard such advice from myself or any other poster. I mean as an animal trainer, would you take advice from a man who repairs bicycles ? Regards to your 'crocs'