A label would never send the original master to another country for their release. They'd sent a safety copy, the same way they don't send the original master to the plant(s) in the US that were doing the quad 8 track duplication and SQ record cutting.
More likely the barcode stickers fell off the tape boxes at some point and no one there can be bothered to trawl through the hundreds or thousands of tapes at the storage facility to find them, especially for a title that might sell a few thousand copies at best.
There were more L&M quad mixes than just Full Sail too, Native Sons saw SQ release in the US toward the end of the quad era, and Sittin' In was a Japan-only SQ release.