If this theory is indeed correct...Why would a company whos elite R&D and marketing entourage who are aware of their large presence in uw photography produce a camera with such limitations - coming after a string of successful compact class cameras in S90 / S95 and G series??? It doesnt stack up.
If you mean Canon? Then truthfully, I seriously doubt if Canon gives a flying flip if their cameras, including the S100, work with the Inon or Fisheye lenses or any other third party housing. They sell quite a few of the leaky, plasti-cases and beyond that, no, they do not care. Not on their radar screen. The long zoom lenses have never been good for use with wet lenses, not on the G series or any other brand of long zoom compact. The wet lenses are by design intended for use with either a 35mm native lens or a 28mm native lens and Inon states that a zoom ratio much beyond 3X is problematic. The S100 is well beyond 3X and worse, it is native 24mm, that means the lens will need to back up (it backs up through about 24mm to 50mm before racking forward to full zoom) quite a bit more than the S90/S95 which do not have to zoom at all with the Fisheye UWL-04 and only marginal 32mm to 35mm zoom for the Inon UFL165AD which I use and many others use quite happily on their S90/S95.
I went to Best Buy for a gift for my niece and while there compared the new S100 directly to my S90, it darn sure looks like it has a longer zoom to me and the zoom rack distance is greater and it is DEFINITELY going to retreat further to be at either 28mm or 35mm which means, can you say VIGNETTING.
If I am wrong, great, but don't count on it until somebody actually sticks the lenses on the housing and says different and show the photos to prove it.
At this point in time, now, what three years past the wonderful S90, not sure the S series would be my go to in the S100 flavor, there are now several other interesting choices available in a similar TOTAL PACKAGE price.
N, ever the skeptic