Sadly like a range of topics, many either just don’t know, or have received false information from others (even other websites or communities) and they think that it is correct.
With Ich specifically I have seen this a ton of times where many state that heat doesn’t kill them no matter how hot (or the temperature it does will fry all of the fish), but this has been proven false in many studies and that heat alone can eradicate it completely it the temperature increase is 15F above when they first appeared (or from the tank that they originally appeared from). Similarly have seen many people note specific medicine is or isn’t invert safe when it is under correct dosaging.