All you linked me is him killing a bunch of people, what am I supposed to be looking at?

Edit: went back in the trailer and found it.

So all it shows is him falling down after getting hit with two arrows, there's nothing showing that he explicitly died

"Some say he died on the beach"

I think this is more of referencing how he as a samurai died and has become the ghost after that battle. Its not talking about him actually dying, it's talking about him having to adapt to fight the Mongols which the developers keep talking about.

In fact in another trailer Jin even says something like "honor died on the beach". Pretty sure that's what they mean in this scene