I bet this guy thought that as well
he's not armwrestler. tendons not strong.
also you shouldnt lift heavy with your arm extended like that. Bicep is not made for Heavy loads in that angle.
you have to be tight. Like the armwrestlers. and not extend the arm too much. Notice he tore it in the bottom portion ofc.
it's like doing super Heavy flyes, with full rom. a pec will tear