I scanned this and I didn’t see a clear explanation of the difference between selecting gray and Jz or L for luminosity but you could try the same parametric mask settings change channel and see what the results would be…
EDIT…not the result I expected …I got a completely different mask…I clearly don’t understand the difference… see the attached file
Jz vs Gray for Luma Mask.pdf (286.6 KB)
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