CQL supports both version-specific and version-independent specification of and comparison to direct reference codes. The best practice is for measure authors to use version-independent direct reference codes and comparisons unless there is a specific reason not to (such as the code is retired in the current version). Even in the case that version-specific direct reference codes are required, best practice is still to use the equivalent (~) operator in CQL for the comparison (again, unless there is a specific reason to do version-specific comparison). As far as I know there are no usages of version-specific direct-reference code comparison in CQL (if there are any they should be flagged and addressed).