Why can I change my QQ password via SMS?

In order to protect the number security of QQ users, Tencent has adopted a password modification restriction system, requiring sending short messages on mobile phones to obtain verification codes. When DNA users modify QQ password, personal account password, network hard disk password, address book password, and QQ mailbox "My Folder" password on the webpage, they will notify users by mobile phone. However, through the password protection and password reset in the complaint form, the mobile phone will not be notified.