I'm sure there are plenty of people that have somehow slipped but I suspect it would more likely be if someone was walking in the bathroom with socks on but whatever the reason, it has been considered for years that high gloss tiles are dangerous in what is called a wet area but I can't disagree with you that a mat is all that is needed to stop from slipping with wet feet but of course people have slipped in the bathtub too because it's so slippery so the jury might still be out as to how to make a bathroom totally safe. I think it's just a suggestion based on some kind of trials and my theory is more hand rails where possible.

Post grouting, and grout drying a fine layer of grout remains. It is easier to remove the next day, by wiping with a soft disposable cloth ( blue roll about $ 14 ) change cloth frequently. I it has been on there for some time, check with tiler if he/she sealed the tiles. If the tiles are not sealed...Tile shops sell grout remover, need to take care and clean each tile..to avoid the grout

Pacific Tiles at Sefton, near the roundabout to Birrong Pool Quality tiles and cheapest prices, tilers buy their tiles at Pacific However Avoid prior to 8.00 am and after 3.30 pm, too many tilers

google "greige stone look porcelain tiles" Yes GREIGE is a colour. https://www.nationaltiles.com.au/concreto-greige-natural or https://www.nationaltiles.com.au/concreto-sabbia-natural which is a lighter colour.