If they already have it why is there no evidence of it in the game yet?

Because it's not in the game yet. They're working on it, as I've said. It's more than just idle claims. They have a full team of netcode engineers, and a consistent 'paper trail' of work going back years, including 'milestones' that they've broken it down into, which they've been working steadily through for a while. I'm not going to pretend I have a high level understanding of it, but it's clearly an extremely difficult task.

I've never seen the type of flawless server meshing

WoW and ESO use server meshing. Server meshing isn't a novel concept. It's the requirements set by the game due to the insane scales involved that's challenging.