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):

hydrateRoot ページに埋め込まれた playground から始め、fork ボタンで開かれる外部 sandbox とその動作を比較します。例を再現し、playground が hydration と初回のレンダリングをどのように処理しているかを追跡します。埋め込まれた例が一時的に "Is Server" を表示してから "Is Client" に変わり、ドキュメントに記載された動作と一致すれば完了です。