The unknown number isn't displayed because, honestly, it was kind of useless, lol!
Seeing "Armor: 28" doesn't actually tell you anything other than your character having 28 armor. It doesn't tell you if that's good or bad. But seeing "Armor: 32%" tells you that all physical damage is reduced by 32%.
That said, I agree with you that it'd be nice to see both. It would only be two more lines in a page that a lot of folks don't really look at anyway, so I don't think it's too much to ask.