Problem is that there are multiple inconsistencies.
1) Are we really serious that we are going to have PROOF of one oil being thinner than another at -20, -30, -40C, based upon only TWO points that are at 40 and 100C? We are extrapolating 60 to 80C away from TWO points that only have a 60C spread?!? While the spirit of wanting to figure out cold performance is good, the method by which it is done is suspect at best, and without some real data proving the soundness (plus typical error), the "curves" shown are totally irrelevant.
2) I have yet to see what A3/A5 have to do with cold low temperature pumpability and flow characteristics. Sure, they specify HTHS, drain longevity, deposit formation, etc., but IS there any mention in the A3/A5 spec with respect to cold flow differences? Sure, we can SPECULATE that since the A3 is a bit more robust at TEMPERATURE, that it may be a but thicker at cold conditions. But this is just speculation. And since our curves are suspect per #1, we don't have a good way to discern, unless we have run the experiments or pulled mfr data from a statistically significant number of samples to show a relative trend across basestocks.
3) Apparent flow characteristics from a freezer test may or may not be indicative of any real results. These oils with VIIs, pour point depressants, etc. may not be newtonian, and so the characteristics of viscosity under shear conditions may not always behave the same. It would be one thing if we did this in a heated/cooled rheometer, but these tests too are suspect.
4) The point that a 0w-40 will be "thicker" at the cold spec temperature than a 0w-30 is merely an artifact of the suspect curve fit processes that are not validated experimentally. Does it make physical sense based upon our limited knowledge? Sure. But is it true? Could depend upon VIIs, and how the oils use pour point depressants and whatnot.
5) Do we have any indication that the oil pressure and oil temperature under operating conditions varies that much for typical US use when the temperature is 20F versus 90F? I know that the real oil pressure gauges in my chevy indicate the same pressure under load regardless of temperatures, and the oil temperature gauges in both of my BMWs both show the same steady-state temperatures regardless of ambient. Sure, under absolute high load conditions, there is a reason for protection reasons, but under gentle use, is there a real reason to vary viscosities based upon ambient? Maybe, maybe not. Using that logic, the selection of A3/A5 may be based upon driving style rather than temperature conditions. There is a lot here that we do not know, and it IS a risk to deviate from manufacturer specifications.
There are a LOT of variables here both in lube designs and physical parameters. There is a LOT of speculation here which may or may not be correct. Posting some suspect curves as rule/law and stating that it is so, and that everyone else is wrong because they are questioning points that are totally suspect is just poor tact and a diversion tactic to take focus away from the lack of correctness in the original assumptions.
Some of the points may have validity, but unless the speculations have been experimentally validated, they are suspect. There is a LOT of suspect stuff here and we should be wary of accepting any of it without at least a bit of additional data to back it up.