What a long thread... I only have personal experience. I bought a brick of Tenex, Match, Target, Contact, SK+, SK LRM so all in the same lot #. I ran 6x5's with my factory T1X. Pretty loose chamber, don't know what it was reamed it, but it showed very consistent results. I have 3 6x5's in Match, Tenex, Target, Contact, etc with it... shot a ton.
Tenex, Average 6x5 - .8" at 100 yards
Match, Average was .9"
Target, Average was 1.15"
SK+, Average was 1.15"
SK LRM, Average was 1.2"
I then bought a new IBI barrel and repeated the 6x5's with the rest of the ammo I had from the same brick.
Target, Average was 1.2"
Match, Average was 1.05"
Tenex, Average was .9"
SK+, Average was .95"
SK LRM, Average was .9"
So quality of the ammo and the ES/SD were the same, but groups widened up and shrunk by about 15% when switching barrels. When people say ammo likes a certain rifle I think there are a few factors.
Headspace - someone had done a few 5x5's with headspacing going from .039 to 0.43 and there was a significant change per thousands of an inch.
Chamber / Feeding - different ammo/lube feed differently. There are some differences in the size, controlled feed V22, great, it goes right in, if my feed angle is from a magazine, and I'm constantly scraping the top of my soft lead bullet into the barrel, that could be a big difference. CCI SV has somewhat longer noses or something. Rim is slightly thicker?
So yeh CCI SV, Lapua, and Eley do have different measurements on their rim thickness and lead bullet. And then when you combine that with rifle's headspace, chambering, and feed angle - I do believe certain ammos can perform better in certain rifles.
I had headspaced my new IBI barrel on the SK ammo, maybe that's why it shoots better than Eley. I could've probably headspaced on Eley, and maybe the reverse would happen. Even though the SK ammo is catching on my barrel and scraping the bottom edge, it still is shooting much better than my T1X factory was shooting it. But I can't get below .9" averages with Tenex, where I was consistently pulling that on my factory barrel. And I've never shot .9" averages on SK+ and I can do that now on my new IBI barrel. So $5 vs $15 a box, I'm happy.