I'm not
I'm not being pedantic, I'm saying I've tried what you're theorizing about, and the equivalencies and generalities you're throwing out as facts are wrong.
I'm saying I've found the real world difference between top end .308 and .30-06 loads is usually closer to150fps, not the 50fps you're stating, sometimes more with heavier bullets. I also haven't seen that difference change much in shorter barrels. So your conjecture about the .30-06 being "too inefficient to burn the extra powder" and therefore not delivering a significant velocity bump over .308 of the same size is just nonsense. There are folks posting real data and experience with shorter .30-06 rifles, but you don't seem to be interested in learning, just doubling down to argue that your initial assumptions were correct afterall.
I didn't see any .30-06 data in the table in your first post, but you said above that your example velocity of a 178gr bullet at 2,560 fps in a 16.5" .30-06 is a measured number right? Is it your load, your rifle and if so what is the load?
Here is some load data from my 18.5" .30-06.
165gr SBT, 59gr H4350, ~ 2,800 fps (was 2,920 fps when the barrel was 22")
Here are some spreads I shot with 168gr TTSX to start load workup.
View attachment 8529203
View attachment 8529204
View attachment 8529205
One of the posters above also mentioned that his 16.5" .30-06 with 165gr ran around 2,725 fps, which is only about 25fps slower than I used to run 165gr NPs in my 22" .308.
For comparison, here are some of my current and past .308 loads.
SFAR 16"
150gr Win Deer season xp - 2,680 fps
165gr TGK, 40.5gr AR-Comp - 2,540 fps
Sig Cross 16"
168gr BT, 41.8gr AR-Comp - 2,595 fps
Tikka CTR 20"
178gr Amax, 43.8gr Varget - 2,605 fps
Maybe your 18.5" .308 runs just 50fps slower than the '06 data above, but I would be surprised as I haven't been able to do it without loosening primer pockets.
Your 24" .308 178gr data above seems to be right around my 18.5" 180gr '06 velocities with 5.5" more barrel. ~30fps per inch of barrel and that seems about right.