Sean Carroll, the author, is a huge proponent and believer [1][1.1] in Many-Worlds Interpretation (MWI) interpretation of QM. MWI's basic idea is that the wavefunction is real and that there is no wavefunction collapse. Each time there's a decoherence, there's a universe split. Some physicists think this is pseudoscience or 'crackpottery' at best [2] since it can never be proven. A lot of physicists also don't see any value in MW's interpretation since it offers no predictive value (if you assume it to be true, there's nothing that this belief 'buys' you).
So when Carroll talks about 'physicists not understanding QM', he's just unhappy that most physicists don't share his view about QM and he's been known for trying to shame physicists for not sharing his view too. [3][3.1]
So when Carroll talks about 'physicists not understanding QM', he's just unhappy that most physicists don't share his view about QM and he's been known for trying to shame physicists for not sharing his view too. [3][3.1]
[1] http://www.preposterousuniverse.com/blog/2014/06/30/why-the-...
[1.1] https://www.youtube.com/watch?v=HxgGYJ3OjM8
[2] https://motls.blogspot.com/2014/07/many-worlds-pseudoscience...
[3] http://www.preposterousuniverse.com/blog/2013/01/17/the-most...
[3.1] https://www.youtube.com/watch?v=ZacggH9wB7Y