1 Rep max for MMA purposes is useless at best and incredibly dumb at worst.
Doing this just tests his strength, it doesn't build anything, it doesn't improve his strength, his lifting form, or produces anything of value.
If you train powerlifting, or you have an YT channel based on lifting, sure, but why would a good coach allow his fighter to risk injury for absolutely no benefit? MMA training still has a lot to go and leave nonsense out the door. He would have benefited a lot more doing 340-350 for 3-5 clean reps, than this ego exhibition.