No they're not. Why would you think that people would not be able to correlate the visual phenomena with the auditory stimulus? The article you link to doesn't even mention auditory phenomena so I don't know why you thought it would support your claim.

Also, please consider that it's extremely rude to just invalidate peoples' experiential claims, although I'm sure you didn't intend your comment in that spirit. Synaesthesia is a well-documented neurological phenomenon and you've just made yourself seem ignorant rather than clever.