I am not sure if this is intended, but, multiple golden whetstones stack additively. So, one gives you 1.25x mult, but two give you 2.5x mult, 3 give you 3.75x mult etc.
Yes, finding two is almost impossible on a standard run, even less 3 or more.
But, given how insanely Endless ramps up, i think this should stay as is.
Also, the game itself easily overshadowed half my AA library of games, i spent more time here than on anything else.