First rewards like it says... "First". They are only claimable once. So if you've reached 6 Path Sennin once, that's it for you, you've claimed all the rewards under that tab, and that tab is literally useless to you now.

What about the 6 Seal Scroll included as well? Not good enough for 6 monthly free scrolls?

And I'm sure about that, cause its written there right in game:
And the reset I think is their solution for people to play in the Arena, though matching may still be little to be desired, and newer servers still haven't gotten the cross server function due to the maturity of that server. I think this still got people to go into Arena. Its not the best solution, but its an improvement from the pre-2.0 where it was pretty dead. I for one don't even do Arena when I got to 6 Path. I literally just do it once or twice a day just to claim my daily rewards, now I do it abit more to climb the ranks and rage quit shortly after. :@