My guess is that the majority of complaints Amazon gets about hyphenation in ebooks are due to poorly converted ebooks, where line-breaking hyphens from a print-formatted source file have accidentally made their way into the ebook. Amazon support is generally not set up spend more than 5 seconds looking at your email, so I surmise that they've filed it into the "yeah fix your ebook hyphens" category and are not reading carefully enough to realize that they've misfiled it.