“The researchers noted, however, that it’s also possible that TOI-1452b is not an ocean planet. They say it could also be a bare-rock planet with an iron content less than half of the Earth’s — or a terrestrial planet with a thin, low molecular weight atmosphere”
or.....or.....or.....ie. they don’t really know much of anything at all.
Well, it is 100 light-years away, after all. I’d be a lot more skeptical if they did claim to know for sure.