does this mean that such a person can write music?

are they predisposed to some sort of hidden or genetic attribute?

Might mean they have perfect pitch or tonal memory.

I think your ear can be developed like any skill.

But it doesn't mean you can write music, just that you hear it in a way that translates into something, either singing, playing, writing, harmonising, arranging, or even just analysing.

I agree with NDRU.