There's a load of assertions that people make about the pyramids that are just wrong but it's a massive arseache to check. I think it was von Danniken who had the theory that the three pyramids at Giza exactly matched the layout of the stars of orions belt and that a shaft pointed straight at sirius. Therefore Aliens.
Except they don't. The relative distances don't match and the angle of the crooked line is wrong. The shaft does point somewhere near sirius but didn't when it was built. There are three things almost in a line though, fair play for getting that bit right.
Even if it was all true it wouldn't have been even evidence of alien involvement never mind proof.
Still he's sold a lot of books and is gainfully employed by the telly and conferences etc. and it's all relatively harmless and a bit of a laugh.