Hilarious in hindsight pool, since the 5th slot is actually a thing now?
Even with the limited choice of items you can put in there?
The "5th slot" is punched into the artwork card, so maybe the illusive 5th slot is yet to come. However, I think it's fine enough for Hilarious in Hindsight.
Update:
And a belated very hilarious in hindsight reminder - now that Musashi Kai 2 is here, there we have it. The true Mythical 5th Slot has arrived.