Can purple Ezreal be used to pay the cost of Deflect?

Ruling: Purple Ezreal cannot be used to discount mandatory additional costs like Deflect. Deflect is a mandatory additional cost on spells and abilities that target a unit.

Nuances:

• You don't have to pay Deflect on triggered abilities, but those abilities will fall off the chain without resolving if you don't pay
• Optional additional costs that work with Ezreal currently use the words "as an additional cost" and "may"