Yeah they don't show the actually canning step it seems, but it looked like they were sorting them into different batches and from my limited experience on packing lines things get big batched.
It feels like you're imagining a system where people are loading cans from sides of tuna, when in reality it's probably much closer to the cans being filled by a machine loaded with a hopper just packed full of large batch tun chunks.
If he'd had sense and morals he'd have stayed and at least tried to slow them down, instead of just rolling over and letting them pick his replacement.
Dude still has nightmares about that shit.