BTW, the 2 Wikidata examples given for "exact match" here are actually Unique Identifiers for the concepts of Soil and Asthma !!!.... So again, I am a little confused in the usages of "exact match" and "identifier" and "Unique Identifier"  (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.)

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.