This comes with asterisk. 6 months is calculated based on the size of their current backlog and current processing speed. Processing speed can unfortunately vary widely, currently it is about 5000 I-129F cases per months. IF USCIS keeps up that speed, backlog will continue to shrink and filers who just now submitted their I-129F approvals might see their action on their case in as little as 6 months. But there are no guarantees when it comes to USCIS and political changes coming next year.