That guide sounds like a joke. From my limited experience, most guides seem unconcerned with what rifle or caliber you shoot and only really care how well you can hit with it. They tend to stray away from being rifle loonies like myself and many of us, and view guns as simple and boring tools to do the job.
You could call the .30-06 obsolete, or you could call it "classic, established, etc." Unlike the case of many of the WSSM shooters not even being able to find brass for their guns. My first center fire rifle was a .30-06, and is still my "go-to," though I did pick up a 6.5 Creedmoor last year to set up as a longer-range option.
Honestly the 6.5 only matches the .30-06 once you get out around 500-600 yards, and the Hornady Custom Lite 125gr .30-06 loads offer less recoil and the same energy and trajectory as the 6.5 does out to ~ 250 yards.
I have a bit more testing to do, but I believe those reduced recoil loads offer almost identical trajectory to a 180 gr Partition full-power load. Same MV and BC, grab the light option for deer, antelope, etc, and the heavy option for moose, elk, and bear, without having to touch the scope.
