There were standard-equipment CDs before the TAM, that's for sure. Most of the Power Macintosh line was CD-standard, only removal was optional. I've never seen a Power Mac 7500+ without a CD drive, and I own over half a dozen of that series (7500/7600/7300) that were all "low-end corporate desktop" purchases, so if they were to go sans-CD, they would have.

I do have a Power Mac 7100 that doesn't have a CD drive, (the original 66 MHz model that can run System 7.1,) so it would appear that the "standard" happened at the 7500.