Draw calls higher on persistent level?

Currently working on a VR project, we’re using a persistent level with 4 sublevels within. The draw calls on the individual levels are almost half of those in the persistent level - even when the persistent level has unloaded all other levels.

We think - for obvious reasons - that this is severely impacting our frame rate. Is this normal? Does the persistent level draw everything, even if the sublevels are unloaded, and how much will this - in theory - impact our frame rate?

As far as we’re aware, meshes should block the draw calls of things behind them. Therefore, even if the level is loaded, we can’t see it, and therefore shouldn’t be getting drawn.

Hoping somebody can chime in, and point us in the right direction.