Values for highly accurate weapons and vetted squads are fairly artificial anyway due to the aforementioned accuracy cap. E.g. the PPSh has a close range accuracy of 0.8. Combine that with the +40% accuracy modifier of Shock troops and you're technically at 1.12. This value will be capped at 1, meaning the calculated DPS gain will only be 25% instead of the promised 40%. But that's not what you will see in game. Your vet3 Shock will likely fight a vet3 Volks or something. The lower RA of the targeted squad will usually push the overall accuracy below 1 (to 1.12x0.77 = 0.86 in our example), which will not be capped and mean that the veterancy accuracy bonuses have the effect that they are intended to have.
Against a newly build Volksgrenadier, the calculated value would be true, but when comparing vetted units, they might not reflect the game properly.
A couple thoughts based off what you said, please correct me where I am wrong. (Mainly about SMG units)
Serelia data is fairly pointless even if it was 100% correct in a balance discussion as it uses a target size of 1 despite RA being the 2nd most important value. Hopefully, for COH3 we get a version that lets us test vs different target sizes.
Soviet units in general scale better with regards to RA than USF/UKF. Across the board most Soviet units get 40% or more ACC with VET compared to the 30% or less USF/UKF get. Normally the argument would be that USF and UKF start with better based stats which would take this into account.
For example Rangers start off great with their 4 Thompsons and great RA of .73 which was made apparent when I tested them against AssG and won everytime. However with VET, AssG RA outscales Ranger Acc and AssG Acc outscales Ranger RA bonus leading to a situation where they perform a lot more similarly then expected. As Axis elites usually get larger RA bonus than 25% this would mean Rangers(and Paras) perform better against mainlines unless Paras use Tactical advance.
Penal Acc bonus may not increase max damage but would make them the most consistent performer against axis Elites as Penals could brute force past Axis great RA.
This also means anything less than 10% Target size buff against most Soviet PPSH is pointless which is why most OST players skip G43 upgrade in short range maps. At VET3, the Gren would receive the same amount of damage from a VET3 Shock/PPSH Con/PPSH Partisan or Penal which makes it a fairly lack luster upgrade vs LMG.
On the flip side, the damage reduction removal was a much larger nerf to Rangers than was advertised as no matter what their is a CAP on the damage certain weapons can do per second as seen with Gren example.