This statement is correct to some extent. Once you make a new ID, start your match, your hidden MMR at that time is 3000. After that, if you get good stats (KDA, damage and stuff), you can jump even 1000 MMR in 1 match. But once you have played almost 50 matches, its then almost fixed. From then onward it works like ranked matches. You win you get points, you lose, you lose hidden MMR too.
I hope this helps.