Makers beware!
Much like with common household chemicals used for cleaning, such as bleach and ammonia, improper use of these can produce e.g. chlorine gas, which while harmful is generally not lethal. Things get much more serious with brake cleaner, containing tetrachloroethylene. As explained in the video, getting brake cleaner on a rusty part to clean it and then exposing it to the intensive energies of the welding process suffices to create phosgene.
I do not weld but could see myself making this mistake without having been informed.
I use brake clean as a basic cleaner for a lot of things in my garage as it does a pretty good job and also evaporates quickly without leaving a residue.
The story tracks my general experiences pretty well
I would guess this mistake is much more common as brake clean is used as a general cleaner by a lot of people