Do you have a source for that, since it seems to be a quote from somewhere? I'm not questioning or challenging you, I actually want to use the link to disseminate this among my companions that use that term for purposes of labeling in trans spaces.
Sex assignment is the official term used for designating a sex to all babies[0] not just intersex ones. As such it is totally correct to use the terms AFAB and AMAB to describe non-intersex trans or even cis people.
The author most likely just has a bone to pick with trans people for using intersex people for their own ends, without sharing their visibility or talking about our issues. Which is a valid grievance, but this is not a valid outlet for it.