Unable to hide code from a Playground Page

I tried hiding code from my Playground page by following Apple's doc: https://developer.apple.com/documentation/swift_playgrounds/hiding_code_from_a_playground_page

However, the following doesn't seem to work when rendering the documentation/playground page. Am I missing something here?

//#-hidden-code
import Foundation
import PlaygroundSupport
//#-end-hidden-code

Tested on:

• Xcode 12.0
• Xcode 11.5