AFAIK 18650s like he's using never swell as they're in hard metal shells not pouches like most consumer electronics, so they don't have the ability to swell until they're catastrophically damaged. He's built a small building 50m away from his house to hold it anyways so it can probably be safely allowed to just burn, it's not like fire departments have much better options than waiting for it to burn out and hoping it doesn't reignite anyways.

> AFAIK 18650s like he's using never swell as they're in hard metal shells not pouches like most consumer electronics, so they don't have the ability to swell until they're catastrophically damaged.

They do swell, but they swell at the terminals rather than at the sides.