Clarification needed regarding dragons

[xenotaff]

Hi,

I just got the dragon booster and reading the rules it says that dragons are immune to fire/flame items. If this is the case why the dragon ass card states that fire/flame items do not work against it if rules says that all dragons are immune to fire?

Also the dragon balls says that they give +5 when fighting a dragon, even one thats usually immune to fire/flame attacks if all dragons are always immune to fire/flame attacks.

Why those cards reiterate what is actuallly obvious? Its not my intension to critize but its something that calls my attention.

Thank you