Experiencing this too with Vulkan, and this seems to not just be related to Nanite.
Noticed when dragging a simple Plane into a scene with Shader Complexity viewmode on:
And here’s a new VR template project shown with 4 different RHI settings, and with nothing else changed:
I submitted a bug report because this seems quite wrong.
To be honest, it feels more like the viewmode itself is reporting inaccurately; the performance doesn’t feel worse in Vulkan than DirectX. But I’m no expert in graphics, thus me submitting a bug report…