I do not have perfect pitch, but I heard that people who have it might have difficulty when a piece of music is not tuned to the usual 440hz pitch standard, it sounds out of tune for them.

But this makes no sense to me, as long everything is in the correct relation to each other why should it sound out of tune? It certainly sounds different, and someone with absolute pitch must easily tell the difference, but why might it sound "wrong"?

This is also very confusing with the notion that perfect pitch is a trait people just have, but the standard pitch 440hz is in essence just an arbitrary definition. So why should this ability be dependent on some arbitrary choosen standard pitch?

Lets make an analogy, most people can see and differentiate colours. Now suppose people define, very accurately on a physical level, what a standard red, green and blue are (like the 440hz standard tone). And from then on every monitor or TV uses just these standard R,G,B colours to combine other colors. Apart from contrast and brightness, the colours on every monitor or TV should then look the same. But then if someone manufactures a monitor (i.e. tunes not to 440hz) the colours would look somehow shifted, but does this imply that the colors look "wrong", or does people then have difficulty using this monitor? I guess not... they just might note that it looks different, but thats all.

I do not have perfect pitch, but I heard that people who have it might have difficulty when a piece of music is not tuned to the usual 440 Hz pitch standard; it sounds out of tune for them.

But this makes no sense to me. As long everything is in the correct relation to each other why should it sound out of tune? It certainly sounds different, and someone with absolute pitch must easily tell the difference, but why might it sound "wrong"?

This is also very confusing with the notion that perfect pitch is a trait people just have, but the standard pitch 440 Hz is in essence just an arbitrary definition. So why should this ability be dependent on some arbitrary chosen standard pitch?

Let's make an analogy, most people can see and differentiate colours. Now suppose people define, very accurately on a physical level, what a standard red, green and blue are (like the 440 Hz standard tone). And from then on every monitor or TV uses just these standard R,G,B colours to combine other colors. Apart from contrast and brightness, the colours on every monitor or TV should then look the same. But then if someone manufactures a monitor (i.e. tunes not to 440 Hz) the colours would look somehow shifted, but does this imply that the colors look "wrong", or does people then have difficulty using this monitor? I guess not... they just might note that it looks different, but that's all.