I know what non-platonic means, but there simpler, yet still non-binary terms to use (though I'm not sure why he went with non-binary in the first place) such as significant other, romantic partner, just partner or spouse. His wording seems really strange to me, like he is trying to technically say he is in a relationship but at the same time hide it in a convoluted way (which would in itself be weird since their profiles are full with shared pictures).
Something just feels off, and I am of the ones that don't think the necessarily fuck around.