New Mogstore "Supply kit" good will or desperation?

[Absurdity]

I don’t remember when it was added or if I’m misremembering, but he’s the guy who hands out the grandmaster caster and world class troller plate items (presumably also the majong one)

Jonathas is about as old as achiements themselves so he's at least existed since 2.0, probably since 1.0 even. Originally you had to visit him to claim any achiement rewards since you couldn't just grab them from the menu itself.
At some point they added the achiement currency, likely when they removed the old veteran reward system and shifted those items into his inventory for you to buy with said currency, slowly adding new items to it.

But the only updates he has gotten to his inventory since 5.0 are adventurer plate kits tied to ocean fishing, mahjong and the rare fish achievement, which most people can't even see.
That's also where my assumption came from that he hasn't been updated in 3 years since I didn't even know he had those plate designs.