Looks like the Audi did actually brake check him, op suddenly gains on him really fast. No need to be braking hard on an exit slip.
However, the fact the Audi is swerving across 2 lanes aggressively moments before and goes on to brake check suggests there has been ongoing road rage prior to all of this and it's all come to a head here. No need for it at all, just pull in begins the golf safely, leave a safe gap and move on. Why on earth try and pass the Audi in that space/situation? It can only be road rage.