alldataback are you experiencing any actual issue without this rule ?
The tutorial seems up to date for beta 8, though some steps seem rather unnecessary. But I'm not familiar with CentOS so maybe they do solve an actual issue. Does the text in Chinese explain the reason this is needed ?
Flarum already comes with a bunch of rules for caching in Apache and those should be all you need, if you have the "expires" module enabled. Otherwise feel free to report it as an issue and we'll see how we can fix Flarum's default htaccess 😉