Guys. Finally got a hold of the mercedes 10L (2.5 gal) OEM DEF / SCR fluid and can confirm it mates perfectly with the MBUSA filling hose which mates perfectly with the Kruse fitting on the car. No spills and no cutting. And best of all it's refillable with bulk DEF!
Got them from ECS tuning
Fluid:
https://www.ecstuning.com/ES1617886/
Hose:
https://www.ecstuning.com/Search/000_583_22_04/