Wano is kinda distant from Fishman Island. Does FI count as a middle ground between Paradise and New World, therefore, a "separate" place?
But again that sentence implies 2 people not born yet by prophecy. Its the same sentence technically and Momo already was 4-6 years old by that point. East Blue actually also fits the definition of a far away sea.
I think its very clear from the narrative that its talking about modern day Joyboy and Poseidon.