SPOILER DUH

Luke does the whole "strike me down and I'll be stronger" schpiel that Ben Kenobi did, and then, just like Ben, magically disappears after getting what normally would be a death blow by lightsaber.

However, it turned out Luke phoned in his lightsaber confrontation, via his magical Force video phone, which has better fidelity than those hologram phones everyone else uses. Clever.

Admittedly they implied strongly in the later movies that Ben died that day, but....are we sure? If you had seen the movies out of order, first The Last Jedi, then a New Hope.....wouldn't you assume that Ben was doing the same trick?