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):

Comienza con el playground incrustado de la página de hydrateRoot y compara su comportamiento con el sandbox externo que se abre mediante el botón de fork. Reproduce el ejemplo y sigue cómo el playground gestiona la hidratación y su renderizado inicial. Se considera terminado cuando el ejemplo incrustado muestra brevemente "Is Server" antes de cambiar a "Is Client", coincidiendo con el comportamiento documentado.