The irony is the left hand injury says enough about the technique, so safe, unsafe, who cares? What is the purpose of making a cut like this? The edge isn't relative to anything, so it won't be square, clean or usable in any measurable way, so besides for show, what is a cut like this for
Ironically their name is "45 carpenter" and 4+5 is 9, which is how many digits he currently appears to have. He may soon have to change his name to 44.
Guys like this usually have names like "Lucky" or "Lefty"