It's not weird at all. One leader was given for free, but, for consistency sake, the slot is still there in the reward book. Only, it offers another premium. Removing the leader slot would be even more strange.
Yes...and that is my problem with it. For 5 RP you get with other nodes much more ressources (3 RP=120 Meteoite Powder and to make Sea Jackal premium you need 100...5 RP is too expensive). Yeah, I know, the game is generous and I don't want to complain, but this seems a little bit strange to me.