I understand it would go against the rules of the RC system, but after all rules are just a mean to an end, not commandments: on the topic of shield values for instance, I would support giving a little shield bonus to plate armor, because, historically, it didn't give a homogeneous protection like mail; on the contrary, frontal plates were thicker to oppose greater resistance to enemy attacks, a measure especially effective against piercing missile weapons.
And BTW I think it's a little odd discussing about the stats' realism... the one that should be in our opinion realistic is the units' behaviour in battle: on this topic, nonhuman units already required exceptions to the usual RC rules.
For instance, armor racial bonuses should be considered "wrong" too, following your reasoning.