Item Age and item PickUpDelay defaults are inconsistent

When using this command:

/summon Item ~ ~1 ~ {Item:{id:iron_axe,Count:1},PickupDelay:-1,Age:-1}

the summoned item will not be able to be picked up, but will have the default despawn time of 5 minutes, i would expect either the item to never despawn or for the PickupDelay to be the default value too.

Thanks