That was a brake test. Max did not have any reason to brake there. All he had to do was go off throttle.
He is trying to be smart and use tactics, but he just doesn't have the experience to pull his dirty tactics off cleanly.
He has mastered cutting in front of other cars to push them off track and overtaking off track though.
For me the last set of races just highlights the gulf in experience and race craft between the two drivers. When you have to depend on dirty driving to win, it's an admission that the other driver is too much for you to manage with your own abilities.
Today the redbull had the faster car, and only lost out because of Q3, and being on the soft tyre the whole race. Also their driver made things unnecessarily complicated for them from Saturday. Max could have won this race if he just kept it clean and be patient.