Are these dual-wielding swords balanced?

I made the following magic weapons specifically for dual-wielding. They are intended to be given out at 5th level.

Placeholder name

Magic weapon (pair of shortswords), uncommon (requires attunement)

Both swords are attuned to simultaneously which counts as attuning to a single magic item. To benefit from the swords’ magic properties, both need to be wielded simultaneously.

Whenever you hit a target with a weapon attack using one of the swords, if you use your bonus action to make a weapon attack using the rules for two-weapon fighting against the same target on the same turn, that attack has advantage.

Whenever you hit a giant with a weapon attack using one of the swords, that attack deals an additional 1d6 damage. For the purpose of this feature, giant refers to the monster type of that name, including monsters such as ogres.

My question is, if this item is a) abusable, b) wildly inappropriate for level 5 or uncommon rarity, c) ambiguous.