The reasonning is that we already have a resolution limit
slider per light.
The global shadow resolution scale is usefull as a quick
speedup option to reduce shadow cost for viewport regular
work or for quick rendering. For final render, the per
light resolution limit is more suited than a LOD scale
since it doesn't modify the filtering of based on distance
from the camera.
This feature is really not hard to add back if there is
a compelling use case for it.
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