BTW, the 2 Wikidata examples given for "exact match" here https://m.wikidata.org/wiki/Property:P2888 are actually Unique Identifiers for the concepts of Soil and Asthma !!!.... So again, I am a little confused in the usages of "exact match" https://m.wikidata.org/wiki/Property:P2888 and "identifier" https://m.wikidata.org/wiki/Q853614 and "Unique Identifier" https://www.wikidata.org/wiki/Q6545185  (I know the differences in the real world...I am just not seeing them applied the same way in Wikidata...and that's why I am getting confused when I am looking at this within Wikidata pages, talk, etc.)

QUESTIONS:

Its seems that Wikidata wants to reserve Identifier's for usages on Objects ? and having "exact match" apply to Concepts ?  Is that a hard and fast rule ?

Where is the original discussions for Identifier in Wikidata ?  Perhaps that's what I need to read and see if there are some constraints on usage on either ? I didn't see any so far.