Our parser/query builder doesn't properly transform independent text expressions (criteria which don't have the "=" sign in the middle). This is visible in the Coverage.
The query to list tickets without a jira with Tests relationship does not seem correct when the search query is 'CR-%'.
It is '\'CR-%\'' AND NOT(JIRA@tests ~ '%') and I guess the below query works
NOT(JIRA@tests ~ '%') AND key ~ 'CR-%'