Dupes retain skill boosts without mastering related jobs. Expected behavior would be that increased stats were not permanent until job is mastered, like decor and food expectations, and special job abilities, like mining abyssalite, etc.
Steps to Reproduce
Start a new world. Either debug or sandbox in a Jobs Board. Assign any dupe to miner. See their digging stat is X+2, where X is their starting stat. Reassign them to architect. See that their building stat is X+2 AND their digging stat is still X+2.
This issue has not been confirmed by a developer yet.