This was a big concern I had reading it. Much of it made sense to me, as someone who has had formal education in basic quantum, and some of it felt very illuminating(the waveform-addition stuff in particular was taught far better than my quantum prof ever managed), but I'm always skeptical of people claiming Truth of a controversy in a highly technical field with no actual training in that field. I've always preferred many-worlds, but I would never claim it is the sole truth in the sort of way that EY did.