Same platform as OP and no mods.
I just ran into this exact issue. However, prior to this, I was actually experiencing an issue where the act 1 fog wasn’t visible on the Travel Map. The fog was definitely still there, it triggered the interactive story sequence that blocks your path in all the correct locations, but the clouds weren’t visible.
For me, the fog visual showed up almost immediately after starting act 2. I can’t remember if the fog was visible the first time I entered the Travel Map or if it appeared after loading my first Travel Map quicksave. Either way, it was within minutes of leaving the capital of my newly founded barony for the first time.
As the OP mentioned, this visual bug isn’t a blocker in the sense that nothing happens when travelling into, through, or out of the areas covered by the fog… but it does make these early stages of map exploration far more challenging as you can’t see any paths under the fog.