SC 1.4.13 Sufficient Techniques

All,

I am trying to understand why SC 1.4.13 on https://www.w3.org/WAI/WCAG21/Understanding/content-on-hover-or-focus.html shows three techniques while the interactive version only shows two. The technique that is not shown is:

SCR39: Making content on focus or hover hoverable, dismissible, and persistent<https://www.w3.org/WAI/WCAG21/Techniques/client-side-script/SCR39>

The other two techniques:
*        @@ ARIA: Using role="tooltip"
*        @@ CSS: Using hover and focus pseudo classes

Which I am assuming are work in progress techniques due to the two @@ symbols. In fact, we did a search and could not find any documentation on this notation. Is the SCR39 a valid technique to use as a test case?

Sean