Went to Harbor Freight and bought their fluid line clamp set with the ubiquitous 20% off coupon and installed it in literally 30 seconds. Six bucks. Even with residual 200F coolant in the heater core it brought the right vent temp down. I saw as low as 40F during a 20 minute drive. Low 90s ambient here today. Cheap fix. 30 seconds to reverse with no tools.
FWIW, Ram is never going to fix this problem, so why wait. How could they really fix it? What are they going to do... redesign the HVAC system on a million trucks in service?
What puzzles me is that this blocking-the-heater-core solution is not uncommon (looking at all the reviews on these valves and clamps being used just like this: to cut-off flow to heater cores for lots of vehicles). You'd think there'd be a universal design approach after 100 years of liquid cooled thermal-engined vehicles to get the heat or even the heater core out of the cabin when cabin heating is not needed. And who among us a half century old or older hasn't faced the issue of heater core problems or inaccessible heater cores leaking in history. Sorry, for the mini rant. At least the AC is cool now! Not quite in the upper 30s as I've noted in my other cars, but close.