I think they can be both and often likes and dislikes develop in utero. DD to this day hates oranges and I couldn't stand them during pregnancy.
that's interesting, when preggy with dd I had bad gastro from.strawberries, never had a problem before, dd is allergic to strawberries and I was but now tested ok again.

so I say fussy eaters are born for the most part, but with all the extras in our food these days, some are made as well.