The introduction of Chaos Vehicles and specifically the "predictable physics simulation that can be replicated over a network" sounds like something they made for Rocket League.
If they have proper physics I'll have to have a look at that, I wanted to try and make my own simracing game in Unreal Engine previously (i.e. use the engine for graphics and inputs etc.), but the built-in vehicles were a step in the right direction but ultimately very hard to try to use realistic physics with.
Does predictable physics mean it can be replicated over a networked game easily?
Yes - but I wouldn't put too much emphasis on the "easily" part. I think that the physics are now pretty deterministic if you run a simulation using the exact same input/setup (on different clients). However, in reality you'd still have to synchronize the state of the objects every now and then (e.g., if a client didn't receive certain inputs on time).