Reading test results also always should be taken with a grain of salt. Production comes always with allowances and scattering. Everyone in engineering knows this that two pieces coming from the same belt will differ slightly. This and knowing that back then the part of manual work was still quite important compared to today's standards should make everybody understand that one assembled plane would behave slightly different from the next one.

So my guess is that the performance will also vary a bit from one plane to another. I don't know how much the allowences were for the different performance parameters but if it was only 1% I would say that it was already high quality.