Beginning several years ago - I'm guessing, maybe 2016 or 2017 - CMS began requiring that MACs price ALL codes in the gapfill process. This has gotten increasingly complex as 30, 40, or more codes enter the first quarter gapfill process.
For example, CMS might say, "Here are six new PLA codes for this quarter, only price them if they are used in your MAC," but in contrast say, "Here are 42 new codes to be gapfilled nationwide for CY2021, please price all of them."
>> (Update). A policy expert at CMS said this interpretation was correct - incidental PLA codes on a rolling basis don't have to be priced by MACs, but the annual national gapfill list is supposed to be filled out completely by all MACs.