This is definitely "a thing" in the Stellar Forge's mindset - it has this peculiar habit of listing Ammonia worlds with no ammonia.
But I think I have the answer...
Whizzworlds
That's what I call the flipside quirk the 'Forge throws at us - Waterworlds where the atmosphere isn't water...but actually ammonia!
Clearly there's some major Magrathea level shenanigans going on here...I'd wager that for every ammonia-less Ammonia world out there, there's a Whizzworld that has the missing ammonia in its own atmosphere. Simples
