The original says 職工保留底缺年資. A quick search through laws & regulations shows that 職工 is variously translated (not a good sign) as employee or worker. A quick search through court decisions suggests that, tax law aside, businesses can define 職工 however they want in private documents, which leaves the question of who does and doesn’t count as a 職工 for civil law purposes open to debate.
So most people are probably fine, but there are always those employers who claim not to be employers… 