Finnish pronunciation would be a dozen times easier for a Japanese person than pronouncing English, but everything else in Finnish is complicated. I won't blame a Japanese author one bit for making a simple mistake. I'm not sure why the Japanese authors commonly don't simply google foreign words for the correct spelling. Maybe it's related to how manga is in 99% of cases (rounded down) meant only for the Japanese audience, so it doesn't really matter. International licenses are a bonus, but they haven't typically got anything to do with the author, the Japanese publisher handles such things, from what I've understood.