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.

從 hydrateRoot 頁面中嵌入的 playground 開始，並將其行為與外部開啟的同一個 sandbox 進行比較。確認初始 render 顯示 "Is Server"，然後再切換為 "Is Client"；當嵌入的範例展示了文件所述的 hydration 流程時，即表示完成。