My guess.
It might not a function of the strings or the guitar but of your hearing acuity.
It seems to me that some musicians, like dogs (no insult intended), can hear things I cannot hear. I have listened to performers continue fiddling with the tuning long after I (or anyone else in the audience for that matter) could detect any discords or even hear any changes produced by knob turning.
I would guess that my ability to detect pitch differences is average. There seem to a few people at the far end of that bell curve.