Hidden and private are two different things though. Clan boards are a clan's own subcommunity within TB, hence the lax stance we have on policy inside them.

TP/VIP is public, despite being hidden. Anyone who buys TP/VIP can see and use those boards, and they're the only boards they get for those subscriptions.

So the only difference is that most people / new people (mostly) won't see slurs being used in a public board. If slurs are allowed in TP/VIP but not elsewhere, then the policy only exists to keep up appearances.