Not sure about logic where clamping the water fixes a/c performance for an a/c leak.
Then you don't know how a vehicle air conditioner works. Let me explain.
Inside your dashboard, you have a large air box that all the ductwork connects to. This houses the blower, the air filter, and various servo actuated doors to direct the air to different vents, the recirc door etc.
This box is made of plastic, and also holds two small "radiators" - the heater core, and the A/C evaporator, which are generally separated by some sort of partition down the middle of the air box.
The
blend door is responsible for temperature. This door moves back and forth to direct air over either the heater core, or AC evaporator - that's how you get variable temperatures out of the vents. Unlike a home AC which is either in heat or cool mode, the blend door sweeps back and forth and in theory can give you 100% heat, 100% cold, or anywhere in between.
The heater core in these trucks always has hot coolant running through it. So the heater core is always at the same temp as your radiator.
Based on the system performance, current theory is that something is wrong with the airbox design or the blend door operation, which is causing air to blow over the heater core EVEN WHEN THE SYSTEM IS IN FULL COOLING MODE. Many members have reported that clamping off their heater core lines causes the air temps to drop 8-12 degrees which is a significant amount, and supports this theory.
This is why it is a "hack" as obviously the system was designed to have both the heater core and AC Evaporator in use. Regardless of what the problem is, people who have clamped off the heater core are reporting acceptable temperatures.