Not to deny your friends experience, but just to shed light on an issue common with chronic illnesses:
People naturally heal all the time from illnesses like this. They just get better with time.
People also get desperate (and sometimes their doctors) and try all manner of remedy.
You get a situation where people who naturally recover end up attributing that recovery to whatever random remedy they were trying at the time. This can be compounded by having bands of people who got sick around the same time, tried whatever flavor of the month remedy was talked about at the time, and recovered around the same time.
Having long covid myself since summer 2020, I've watched this play out more times than I can count now.
This happens all the time with sports overuse injuries also. Kinesio tape, acupuncture, chiropractor adjustments, heat, ice. People try all kinds of things, eventually you get better. Whatever you tried last seems like it helped. But who knows.
I started nicotine after reading through the (probably shoddy) studies on the topic and reading through the anecdotal reports of others experiencing relief with it. (I was desperate, have tried everything I can get my hands on + every kind of dietary intervention.) The experiences seem to be pretty mixed but at least for my form of LC it has made a substantial positive difference.
Out of everything I've tried the only other step I've taken that has made a noticeable difference for me is quitting caffeine. During my acute infection phase it was like a switch flipped that hasn't yet flipped back which completely changed how my body reacts to it. Took me forever to wean off it but doing so has also been a net positive.
People naturally heal all the time from illnesses like this. They just get better with time.
People also get desperate (and sometimes their doctors) and try all manner of remedy.
You get a situation where people who naturally recover end up attributing that recovery to whatever random remedy they were trying at the time. This can be compounded by having bands of people who got sick around the same time, tried whatever flavor of the month remedy was talked about at the time, and recovered around the same time.
Having long covid myself since summer 2020, I've watched this play out more times than I can count now.