I agree. It would be appalling if only the AI or only human players could use some upgrade mechanisms, but both can so I don't see much of a problem. Arguments from realism don't amount to much when you can, for example, upgrade pikemen to ATs, and you can see future techs, civics, and details of the score of your opponents in the world rankings etc. Cherry-picking one peculiarity and ignoring all the others in the game is like some hilarious weird form of wilful blindness. That would be very reasonable if units were treated as being comprised of actual individuals. But they're not. To me they are more like different types of pressure applied to different regions during the game. You might view them completely differently, e.g. A scout is just one man who cries when his trusty dog Old Yeller dies.