i agree that they're not the best sign of reading pressure, but thankfully the article addresses issues beyond just reading primers - including but not limited to...
extractor swipes
extractor printing
ejector imprints/rings
pierced primers
case head separation
neck splits
primer pocket expansion
blown primers
primer flattening
primer cratering
heavy bolt lift
as well as a couple examples of false positives of pressure signs - as well as a perfect example of a false negative (the 46gr example)
as it relates to the 450 bushmaster - we've got a known proof point of case head growth as one of the best ways to read pressure signs in this caliber, but it also takes some relatively precise speciality tools to measure it.
so i think that while its not the end-all-to-be-all on reading pressure, this article can be immensely helpful to those who are relatively new into the reloading hobby - and possibly even some of us who have been around the block a few calibers