People vary in height throughout the day due to spine compression. You are at the tallest in the morning before your spine has had time to compress. Adults get shorter as they age largely due to the same phenomenon taking place over many years.
But I think that says “average human” and not “average height”.
The overarching answer is “people are different”. But I suspect you want a more granular answer than that.
Depending on various factors like age, sex, hydration status, disease process, etc., some people’s skin is more elastic than others. People also have different pain tolerances. If you mix and match all of these factors, you’ll get people reacting differently to the same stimuli.