Handling different client and server content - not showing initial render

In the hydrateRoot page, it is mentioned that
"This way the initial render pass will render the same content as the server, avoiding mismatches, but an additional pass will happen synchronously right after hydration."

which means that the initial render on the playground should show "Is Server", but it shows directly "Is Client" which is very confusing for learners and doesn't show the real behavior.
I tired opening the sandbox in external window, and it indeed shows "Is Server" first and then changing to "Is Client" as expected.

In the Website:

In The sandbox (using the fork button):

Start with the hydrateRoot page's embedded playground and compare its behavior with the external sandbox opened through the fork button. Reproduce the example and trace how the playground handles hydration and its initial render. Done means the embedded example briefly shows "Is Server" before changing to "Is Client", matching the documented behavior.