That groove in addition to letting the grease out will let water and grit in! Neither is good for the ball joint. I see early life failure.You spent $750 for the UCAs, this is a whole kit in the $600-$670 price range which includes an UCA and all the spacers needed.
I have ran the Delta Joints and IMO they are kind of gimmicky. There is no seal on the bottom and the grease groove in the ball joint just allows grease to pour out the bottom without it being sealed. So it was always messy around the joint. They are not close to being a uniball setup, more so a fancy looking ball joint that isn't as good as a traditional ball joint since it uses a rubber washer as the "spring". I cut it apart after running it and was less than impressed. A MOOG ball joint has a sintered metal bearing and a heavy duty spring washer versus a rubber O-ring. I took them off and went to a traditional ball joint. Just my opinion.