Unfortunately all camera actions are still client-side. The camera entity is not networked and it's values are not CRC'd in any way. There is also no camera data in replays.
The "Follow player" feature is implemented by centring the camera on the last action a player performed. For example, if the player gives a move command to a squad, the camera centres on the destination of the move command.
Note that squad selection (what units the player has currently selected) is also not networked or stored in replays, thus the "Follow player" feature does not move the spectator camera as the player selects and deselects units.
I haven't tried the new mode but my understanding is that the replays do now contain the original camera inputs as relic stated that they did this to track if the sound bug was caused by a combination of camera movemenabd game events. I hadn't thought about the network side but it wouldn't be much data to add
My assumption may be wrong