VRF for leader selection

I’ve read on some blog that Aptos are planning to use VRF in order to select a leader for the HotStuff consensus protocol (it is part of the Pacemaker). Does anyone know how exactly VRF will be used in this case?
Usually VRFs are used in order to send a message and a proof that you hold some role (for example, a block proposal and a proof for being the block producer). However, in HotStuff all nodes need to know the identity of the next leader in order to send the NEW-VIEW/VoteMsg to that leader, so it is not clear how to use a VRF… Does the next leader must broadcast a proof some pre-defined time before the next slot starts, proving it is the next leader? If so, what is the point of using VRF? What extra security does it provides?