I'm not sure if I missed something crucial (or several things?) but this seems to be entirely an essay on how SMS is an antifactor in authentication. That they're using Apple devices and services doesn't seem to factor in to it.
what is wrong with SMS? I don't see how it is easily compromised.
Theoretically, someone could exploit a vulnerability in the SS7 [0]. I’m not sure how common these are in the wild, but it had happened before.