I've never said the change was immediate, though even if they used the good oil I would still pick up on minor changes.
Like simpletool said, our 5 senses are amazing. I pick up on things wrong with my car that while may not be anything major at all, are certainly there. Even things like what I'm feeling through my right foot on the throttle compared to my left foot on the rest might raise an eyebrow for me. Not entirely blaming it on the oil, maybe even I'm a little pedantic and pay more attention to my senses after an oil change hence why I might notice these things more.
Though for something like lifter noise, I can guarantee you that has arisen since my last oil change. No ifs or buts about it, this oil has conveniently lined up with my lifters making noise be it the cause or not.