The mechanism of runnable Go examples in pkg.go.dev

Question

There have two examples:

1. fun Marshal: You can see the example are not contain any button.

   source

   func ExampleMarshal() {
       type Item struct {
           Foo string
       }
   
       b, err := msgpack.Marshal(&Item{Foo: "bar"})
       if err != nil {
           panic(err)
       }
   
       var item Item
       err = msgpack.Unmarshal(b, &item)
       if err != nil {
           panic(err)
       }
       fmt.Println(item.Foo)
       // Output: bar
   }
   

2. func Reverse well it has three buttons: Share, Format, Run

   source

   func ExampleReverse() {
       s := []int{5, 2, 6, 3, 1, 4} // unsorted
       sort.Sort(sort.Reverse(sort.IntSlice(s)))
       fmt.Println(s)
       // Output: [6 5 4 3 2 1]
   }
   

I don't understand why one has buttons, and the other doesn't? Does the content (godoc) rendered have anything to do with the version of Go used in the repository?