From what I can tell in reading the ad ... it says only that this canner works on flat top stoves. The issue isn't whether the canner will work on flat top, but whether the heat and weight will crack the glass, turning a fun fish preserving project into an expensive nightmare! I've done it a few times now on the the glass top, and no problems YET, but I'm leery of doing it any more knowing this possibility. Cheaper to get a little hotplate and do it outside...less stinky too. ;-)
The box and instructions for my canner specifically say safe for glass top. It was more expensive than other pressure canners for that reason. From what I understand the bottom has grooves in it to allow for air to flow between the canner and the glass.
Apparently there is some sort of adapter ring that you are supposed to use on the glass top stoves.