4G-AC53U: Parental Controls Really Block All Internet Traffics?

[RRN]

Hi, I am using 4G-AC53U.
When I turn ON "Parental Controls" to block a client's Internet access, does the router really block ALL kinds of Internet traffics including system's service (such as OS update checking, license checking, etc.) ? Or it only block normal user's access, e.g. web browsing, video streaming, etc.?

Thanks.