Apple's "unified memory" marketing is so strong that even tech literate people seem to have this misconception!
They have managed to pull this sort of thing off many many times. https://en.wikipedia.org/wiki/Reality_distortion_field
Having unified memory is a real advantage though, it's not a reality distortion.
Yup, the only reason Macs have higher memory bandwidth is because they use more memory channels, which gives them a wider bus. Both Intel and AMD only allow more than dual channel memory on server class processors these days.