Upon closer inspection, there does appear to be a little head tilt but not enough to explain the asymmetry. Here is a picture of the slice that shows the largest section of the lateral ventricle on the other side:
It’s way smaller than the largest section on the right hemisphere.
Here is a comparison of the largest versions of the lateral ventricles from the sagittal view:
So, there is some asymmetry, but who knows if it’s relevant!
By the way, my neck visibly slants to the right, so that is possibly why one hemisphere seems to sag down in my skull lower than the other one when lying supine.