Versions of the pusher urban legend have circulated for years in different locations. It's good tabloid fodder.
People who go missing in Cardiff almost always seem to turn up in the River Taff - it happens at least twice a year - but no such rumours circulate here.
A body of water makes everything worse - a trip turns into a drowning, and then a massive, well publicised missing persons case before they're eventually found. If they'd tripped, hit their head on the pavement and died then there wouldn't be any real publicity at all.
These claims of a pusher never seem to be accompanied by stories of people being deliberately pushed but surviving - you'd expect at least some to be strong enough swimmers to escape.