This definitely reeks of intentional stupidity and bernard and styro are both part of the group of maker youtubers who are openly doing whatever it takes for views.
That said, this one is at least somewhat plausible. Someone cleans a part with a small amount and a scrub and figures that they'll just burn it off because they are lazy and don't care about residue ruining the weld. Whether that will be enough to be meaningfully harmful is an open question
But I can't think of any situation where you would need enough solvent to remove the rust AND not wipe a part down because it has been soaking for an hour before you took the wire brush to it. At which point this is mostly in the same realm of "only weld in well ventilated places and consider a respirator under that mask" which everyone should do but nobody does.
There are isolated cases of EVERYTHING. People will do anything with everything and that is why OSHA et al are such complicated messes.
Its the difference between possible and plausible.