Why is function.call.call not a function?

Code:

let fun = x => x * x;
-> undefined
typeof fun.call.call
-> "function"
fun.call.call()
VM251:1 Uncaught TypeError: fun.call.call is not a function

      

        
        
        
      

    

Why is fun.call.call

not a function when typeof fun.call.call -> "function"

?