I wonder how large a difference in the SRA needs to be before it is perceptible. Given the range of SRA of a cutter head is 3 degrees (91-94), a fixed SRA of 92 will be out by up to 2 degrees. If one uses a tonearm with an Leff of 300mm, a 1 degree change is 5.5mm in height, which is orders of magnitude greater than the difference in thickness between a 120g and a 200g LP. If it is true that one can hear the difference between LPs of different thickness, we are then talking about a difference of a fraction of a degree. In that case, the variability of the SRA of cutter heads used to cut different LPs will make the whole exercise moot.
And yet small changes can be audible.