Didn’t Intel also try to brand the 64bit x86 extensions as ia-32e initially? Seemed like wasting an opportunity to me.

(Disclaimer: I work at Intel but this was way before my tenure.)

It was because IA-64 was a completely different unrelated architecture that until AMD succeeded with K8 was "the plan" for both 64bit intel roadmap and the roadmap to kill off compatible vendors (AMD, VIA)