Thanks guys.
When I racked my brain for an example of a character with shield and bow, I came up with Lurtz.
I looked him up, and he doesn't get the defense bonus in his profile for having a shield, so I came to the conclusion that not getting the bonus is indeed a thing.
I didn't know that. I was totally a detective.
Being equipped with a bow or two handed weapon, means that just "owning" a shield means the model can use it less well. It doesn't have to make sense, it is just a thing in the rules, and that's how it is. Now I know.
(I now notice several threads here about Lurtz' profile, hehehe)
Of course models with shields and bows/2handers can still use "shielding", but I was scratching my head a bit when comparing banners with shield rules. "Encumbered" from having a shield is very different to the encumbrance of having a banner. Yes, elf blades still split drawn fights, which is something... Cool.
So, if a models are equipped with a hand weapon as standard, but also have a two handed weapon or bow (for some reason, hypothetically), and a shield... they can never get +1 defense for the shield. Even if they use hand weapon and shield in a fight, they can't gain +1 defense. Even if they are being shot at, they don't get +1 Defense.
This was indeed the right place to post my silly question. SBG is not an RPG.
It's a fun game. It is what it is, it's fine, and it is small.
"That doesn't make sense to me, but then again, you are very small."