Actually, this probably is a bug. If the numbers posted are correct, lets look at the lancer example.
Base HP: 350
FU1: 750
FU2: 770
The difference is 20 hp. That corresponds to a base upgrade of 5.7%. There is no tech that upgrades 5.7%...
MY THEORY:
Royal guard units get a different upgrade system than the normal units. For example, the guard upgrade for normal hussars says it is 30% of base, but the royal guard upgrade says it is 10%. The only way that the RG would be better than the normal upgrade is if it is based off the current upgrade level (veteran). So when you upgrade to veteran you get 20%, then when you upgrade to RG they stack.
The question is, does playing cards or researching armory techs before buying the RG upgrade result in a bigger upgrade?
I think this is a cool way to make RG units even better than normal, and it explains why the upgrade costs so much more.
EDIT: By the way, that website does not calculate royal guard upgrades correctly. According to that site, Guard musketeers have more hp than Redcoats. I know for a fact that in game Redcoats have more.
Counter the attack, then Counter Attack!!![This message has been edited by justiw (edited 03-16-2006 @ 05:03 PM).]