Some of that disdain was Elmer resenting Jack's superior education and his having scored the prize job of being shooting editor at, Outdoor Life. Askins resented Jack for replacing his father at OL.
O'Connor was a superb writer and found the .270 very effective. But many forget that he also owned and used .338, .375, and .416 rifles. Had two 7mm Remington Magnums, too, one a fine custom rifle. But he felt the .270 could do most of that work with less weight and fuss.
We need to acknowledge the impact that Warren Page had in promoting 6mm and 7mm Magnum calibers. He was a former master in English at a private school, and was shooting editor at, Field & Stream.
The reading I have done pretty well agrees with what you've said. Jack did load and use both the '06 and 7mm rounds.
He used Springfield and Mauser actions. The M-70 gave him the best of both worlds and came ready to use from the factory.
He also liked 2 WBY cartridges, the 257 and 300. My gut feeling is he did not like being part of Roy's marketing plans.
If Rem had brought out the 280 operating at higher pressure like a 270 their 7 mag would not have been necessary, but the 7 mag set the world on fire until handloaders discovered they could get similar performance in the 280 with less powder, recoil and weight.
The biggest change today is better constructed bullets. Yes the 280 has a larger selection but for most of what both bullets do, the game will never know the difference between a 130 277 or a 140 284 using Nosler partitions for example.
I shot a deer several days ago with my Win pre-64 M-70 (for the O'Connor fans) in 270. Hit it in the heart while it was moving in a fast walk. Dead center of the heart. It was a Sierra or Speer 130 grain bullet in a high velocity round, 200 FPS faster than the factory speed. It went thru the heart and did not open till it hit the far rib cage. I watched it run flat out for 75 yards until it fell dead.
On that shot I could have used, fill in the cartridge, anything and the end result would have been the same. I have made the same exact shot with many other calibers.
The only difference is I like my old M-70, it was my Dad's, it is accurate and has a built in lure for buck deer.
Dad loved his 270, but he was an engineer and read all he could on cartridges/ballistics, when I was young he wanted me to get a 284 Winchester. He said it should do all the 270 can and more.
I never bought a 284 but now have 2 Kimber 84's in 7mm-08, it is pretty awesome for a short feller.
There are many cartridges that all are close to ballistic twins, all fit in that middle ground mostly for Deer, 243 to 30-06 and I think the only real difference is the marketing kool aid given to us so we will be interested in buying another gun.