You're being biased by the climate in the US. A lot of union rep would give free legal advice to nonmembers, especially for small and common things such as clauses in employment contracts.
I would have guessed that most union reps consult lawyers when they finalize a contract and don't have the law background needed.
I think the best way to describe danish unions are that they are a mix of us unions (that i don't know that much about) and law firms for worker.