The shower pan is actually sloped towards the drain 1/4 inch per foot. You visually can’t see it from the photo, but the pan does slope downwards and the water is rapidly draining. No water comes out where the door or the panel are. We do many of these in retirement communities, so you can pretty much shuffle in and shuffle out of the shower without having to step up or step down.

Can it work with a sliding shower door rather than a swing door? I am far away from you in New England but I do appreciate the help

Yes, we do both. I like the sliding, it allows you to have a rug to step onto when getting out of the shower. Usually, the door swings in and out, but the outswing will not clear your rug. The bottom of a hinged door has a seal on it, so there is no clearance for the rug.