Resources overlay does not properly hide resources on top of other resources

See this where limestone is on top of sand. Deactivating the display of limestone does not hide it where it is on top of sand.
Does hide it if you hide both.
Hides the sand under it properly if only hiding the sand.

I think it's intentional to make one realise that the resources
underneath the disabled ones aren't actually on the top level &
make that person think that it's just available for mining right away.

Oh, i see what you mean