Thanks everyone for your input and @Haukeli great job for finding that post of Djozz’s test - thank you. It’s great to see someone else’s numbers to know I am not entirely lost lol. At any rate after looking at Djozz’s results, I have just rerun my test not just with 219b but also with 519a in my S21D using 60 Bead TIR optic, and could now confirm with near certainty my result 
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For Convoy S21D with Nichia 219b 4500k:
1. No lens: –0.0127
2. Convoy AR Green-reflection lens : –0.0124 CCT 4471
3. Wurkkos Non-AR: –0.0123
4. UCL AR Blue: –0.0123
5. UCL AR Purple: –0.0102 (the Purple Lens’s Duv is “20 points” (0.0020) more positive) CCT 4365
Note that we know changing lenses affect Duv, but not frequently mentioned is it also shifts CCT about 50-100 points.
Where my result is different from Djozz’s - I found essentially no significant difference in Duv among set-up 1 to 4 above.
Where my result is similar to Djozz’s - The UCL Purple AR turns Duv approximately 0.0020 more positive (note the decimal point) and drops CCT roughly 50-100 K versus the group of 4 above. Not a huge change numerically, but definitely there, and does bring beam into more yellow-green territory.
