We are longer on average now, so I'd argue size 47 is also more common now though. Making the 'it's just one guy'-theory even more likely.

That is a size 13 US which is a relatively common shoe size among men with big feet. Looking at the photo I could tell it was about the size of my shoes.

A mens shoe isnt really particularly large until you get to the limited sizes, like 14 or 15, where dudes have like two shoe options to choose from at any given shoe store. Pretty much every mens shoe is made in sizes up to a 13 consistently

11.8 inches is about a foot.