Looking at the review paper cited in this article[1], the authors all seem to be actual doctors, in fields such as pulmonary and critical care, working at hospitals and medical schools - not "armchair doctors".

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8088823

> Dear Dr Marik I am from a remote place(Muzaffarpur,Bihar) in India.people are not that rich and can’t effort costly treatment.i used your MATH PLUS protocol in TOTO to save hundreds of life at very low cost.since there is limited govt facility I have managed pts with SPO2 of even 72% at room air with home oxygen,proning and MATH PLUS. I don’t have words to thank you for this.you deserve to get Nobel Prize for your protocol. Words are not supporting me enough to thank you. Dr Vimohan Kumar

Source: https://www.mountainhomemag.com/2021/05/01/356270/the-drug-t...

Sounds like he was in the trenches, not an armchair.