Further to the issues in #1, the certification reference is at:-
AC 20-167A
https://www.faa.gov/documentLibrary/...AC_20-167A.pdf
This supports the view that the accident aircraft did not meet this guidance; perhaps the reason for the warning, but that may not avoid instinctive use of a compelling display.
Also, that although the regulatory guidance for synthetic vision appears similar to conventional instrument hazard assessments, it may assume too much about pilot involvement. Without a comparator system or stand by 'instrument' for synthetic vision, then the crew has to detect and resole a failure condition; choosing between a 'real world' display and the EFIS attitude indicator.