Reverse Daylight Detector Not Emitting Full Redstone Signal

When the Daylight Sensor block is set to "Reverse" mode, it does not fully emit the full 15-block redstone strength when there is max moonlight. It maxes out at 11 blocks instead of 15. This happens for a daylight sensor with nothing above it except Air blocks and weather is not running.

Tested also with "Normal" mode on the Daylight Sensor and it is able to give the full 15-block redstone strength.

See attached picture for visual example using Redstone Lamps to represent the redstone strength and clock in hand. Note: Comparators used were not in the "on" position.