What is the difference between the following subject headings (Cf. bib (OCoLC) 52442717) vs (OCLC) 150835830)?

Athena c (Greek deity) v Art v Congresses
Athena c (Greek deity) x Art v Congresses

And (Cf. (OCoLC) 45539635) vs (OCoLC) 466762391)?

Athena c (Greek deity) v Art v Exhibitions
Athena c (Greek deity) x Art v Exhibitions

The SHM instruction under H 1110 $v Art seems to have been causing this problem on a massive scale in OCLC. The second part of the sentence where it states [Use for]  or works for discussing such art is perhaps the culprit. This part actually refers to the use of $x Art (lccn sh 99001934) and not $v (lccn sh 99001267).

For the sake of clarity, why not insert $x Art somewhere in the text?