Armour values

I noticed that some units have quite weird armour values - when compared to other units who have the same armour.

Example:
Cohortes Reformata: 10 armour - Lorica hamata & Montefortino helmet
Cohortes Praetoriana: 10 armour - Lorica hamata, greaves & Imperial Gallic helmet
Cohortes Imperatoria: 12 armour - Lorica hamata & Coolus helmet
Cohortes Evocatae: 14 armour - Lorica hamata, greaves & Imperial Gallic helmet
Antesignani: 14 armour - Musculata & Coolus helmet


Seems to me the armour values of the Antesignani and the Cohortes Praetoriana are wrong, or did I miss some important facts? :idea2: