Going to make this as short as possible.
Oil wedge is better maintained at higher RPMs. These 6.2l rarely exceed 1700 RPM on the highway under most driving conditions.
Oil wedge is typically better maintained with higher oil pressure. These 6.2l have around 25-28 PSI warm oil pressure in drive, 35 PSI warm oil pressure at idle and around 45 PSI warm oil pressure when cruising. The 5.3l has around 60 PSI at 1100 RPM.
Oil wedge typically is more robust with a higher viscosity oil at lower RPM's, higher oil temperature as well as higher RPM's.
GM screwed the pooch with the 6.2l when compared to the 5.3l when it comes to the L84 vs the L87 and oil pressure. GM should have probably put the same oil pump from the L84 into the L87, BUT they chose to do something different.
The L84 5.3l oil pump puts out more pressure at lower RPM's and DOES NOT have the 2nd stage solenoid control that the L87 and predecessors had. Based on all my testing the 2nd stage oil pump solenoid is not controlled by engine Load but by engine RPM. Seems that the 2nd stage is typically not triggered until around 3500 RPM. Oil pressure jumps to around 75--80 PSI when the 2nd stage is triggered. Seems the 2nd stage might be better triggered at 75% and higher engine loading.
0W20 has been used successfully in many engines, BUT the majority of these engines are not pulling a 6000 lb brick down the highway at 1500-1700 RPM with many spikes in engine loading from 70-100% on a regular basis. Add to this the DFM turning on and off cylinders and probably causing crazy crank loading and vibrations. Also assume this loads the thrust bearing more due to crank walking.
Many of the other engines running 0W20 do not have AFM/DFM systems, most of the smaller displacement engines rely mainly on variable valve timing, DFCO, Auto Stop/Start for fuel economy bumps.
The variable displacement oil pump can be problem depending on the oil filter flow restriction. The oil pump modulates or regulates the oil pressure based on the oil pressure build up on a spring inside the vane style oil pump. If you happen to use an oil filter that is too restrictive, the oil pump is fooled to think the oil pressure is correct and backpressure causes the oil pump to modulate or regulate the oil pressure before it even get out of the oil filter.
All this talk about the difference in oil cooling between 0W20 and 0W40 is nothing but noise. If this engine was in a race situation running 7000-8500 RPM non stop, then it might make somewhat of a difference. I believe all the 6.2l engines have a radiator based oil cooler anyway, so this along with a larger oil sump capacity this issue of oil cooling is again, nothing but noise.
The Corvette and the Camero with LT1 which is effectively the same engines are speced for 0W40 by GM, so why the difference? They sell far more trucks with 6.2l engines than the Corvettes and Cameros, has to do ONLY with CAFE and trying to avoid fines.
In general running 0W20 has less of a margin for higher temperature, fuel dilution, low RPM lugging, less shock and cushioning ability and will not tolerate surface finish and wear as well as a higher viscosity oil.
Take a look at these 2 pictures of GM oil filters, one is the OE PF63 and the other is the UPF63R Delco Gold filter. Understand that there is a REASON that GM has so many larger oil intake holes in the PF63 oil filter. I do not know the full reasoning behind this, but part of my thought is to allow better oil pressure charging with the Auto Stop/Start nonsense and overall less restriction on the filter inlet. Additionally the PF63 probably flows better than the UPF63R based on the oil filter media. Regardless of how great/fine the oil filter is, the oil keeps dirt in suspension and the primary way to get dirt, soot and other small particles out of the oil is to change it! Changing oil often is far cheaper and easier than an internal engine repair.
If you are so worried about oil filtration, install a bypass oil filter and use the PF63, you would be far better off than screwing up the variable displacement oil pump performance and operation.
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Overall I think the debris in the crankshaft and on the connecting rod story is a red herring bunch of BS for GM. If the issue was just the crankshaft tolerances and final finishing, then this pretty much makes GM guilty of VERY POOR quality control and inspection which is really what happened here that there is 4 model years and probably close to 800,000 engines that have some degree of problems. Understand that GM is not counting all the replacement 6.2l in the numbers for the recall.
So everyone will do what they want, think what they want and make all sorts of claims, but the bottom line is GM tried to squeeze too much fuel economy out of the 6.2l in the 6000 lb bricks and it comes with a price and sometimes a very high price. Lots of talk about people not wanting 4 and 6 cylinder engines in vehicles this size and I fully agree, no interest in a Ford Ecoboom or the Jeep/Dodge Hurricane 6 cylinders, you think the 6.2l has problems!!! There is no way the smaller engines will last hauling large vehicles, its asking too much from the hardware and the engine oil.
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