i couldn't speak authoritatively about what happens at the factory, but i will say of all the PSS and P models I've seen over the years, not a one of them was a lemon. they were all shooters where the SPS stuff seems more like 60/40 or so. my personal sample size is large enough i am pretty sure there's something different, but not large enough I'd say i couldn't be just really lucky
there could be differences in assembly, or QC or other stuff, not just the fact that they came off the same line.