The "glass" stove tops are not really a true glass, but they are a glass ceramic composite material. I have not seen a "do not use case iron" notice for them, but Whirlpool does caution not to slide rough cast iron as it "might" scratch the surface. I don't think it would be a good idea to drop one on the surface either, but that is pretty much common sense. I think if I dropped one of my hand sledges on any stovetop it would damage it, so I would expect no less from a similar weight be it a cast iron pan, a brick or whatever.
We have been cooking on one since 1998. That stuff is tough as nails and easy to clean. They make a special abrasive cleaner, but sometimes when stuff boils over and cooks onto the ceran surface, it's just as easy to take a single edge razor to it and scrape it off before hitting it with the cleaner.
And yes, I have an assortment of cast iron (raw uncoated, not the enameled cast iron) and I cook on my Whirlpool cook top all the time.