nah i dont think the author went so far into messing with his readers... there are very few mangakas out there that plan plots from beginning to end before even writing a chapter, and IMO UnM was no exception. Usually mangakas make it up as they go, and us readers are lucky if the author can think 10-15 chapters ahead. He probably planted that little reference for further use in case he wanted to explore the mystery of the island later on, but then he turned for more ecchi stuff for some reason, hence the actress from mainland and the solo experiences with the maidens.
I would have expected an "unexpected" (pun intended) trip to mainland, maybe a confrontation with Negi's father, and to have a dip into (to us, still unkown) Negi's life before the island, maybe a best friend from middle school, maybe his first crush, something to know about his background. We got nothing, that's all doujinshi material now. All we know is the various degrees of the maidens' love for him (even though they dont know almost anything about him, just like us), their troubles with unknown feelings, and that pretty messy part about the Dragon festival.
As i wrote before, i preferred AyA also because it was more coherent, complete and round from a narrative point of view. If you pluck some filler here and there, you could say that the plot was though with some time in advance (at least as soon as the continuation of the manga was confirmed)
Edited by maffa, 19 March 2014 - 08:51 AM.