To be fair, going from cacao fruits to chocolate takes a lot of non-obvious steps (getting the seeds, fermenting, drying, roasting, etc), so I don't think it's completely unbelievable to imagine people wouldn't know chocolate, especially if they don't have a lot of sugar around. Then again people find the craziest ways to eat the
weirdest things.
I agree with your point about finding the trees in pseudo northern Europe. Sometimes the author at least tries to say that it's in the southern part of the country (presumably warmer), but then the people still dress in pretty much the same way...