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.

从 hydrateRoot 页面中嵌入的 playground 开始，并将其行为与外部打开的同一个 sandbox 进行比较。确认初始渲染显示 "Is Server"，然后再切换为 "Is Client"；当嵌入的示例展示了文档所述的 hydration 流程时，即表示完成。