shōu wěi bú shì kè tào, tā gào sù duì fāng zhè jiàn shì zàn shí jié shù le, bù yòng jì xù děng nǐ de xià yī jù

收尾不是客套，它告诉对方这件事暂时结束了，不用继续等你的下一句。

The closing is not just being polite; it tells the other person that the conversation is over for now and they don't need to wait for your next message.