And what the issue with current system, when you can read the veterancy when choose the unit (except text inside)? Lurking throw steam, especially during the multiplayer battle, not the best option here.
Adding encyclopedia in the main menu can be a good addition for "watch and learn" section. On the other hand, there is extremely small chance for changes like this. Even fixing strings and addings exact veterancy to "stars" on the unit's portrait seems more realistic.
I am under the impression that Relic has no provided more detailed info because it greatly increase the work load of patches.
A encyclopedia/library could get stat from units from the files automatically.
I would prefer the in game description to be more accurate but I doubt it will change.