Have a good read of O-S's comprehensive explanation at #1
There are 2 solutions -
(1) Leave the 35 ft screen height in place for all operations, and suffer a huge loss in payload (and I mean HUGE), or
(2) Legislate allowing for a lower screen height (15 ft) for Wet Runway operations.
The legislative process has opted for the 2nd choice, i.e. the 15 ft 'line in the sand' Vs the 35 ft 'line in the sand'.