Why does apple change the resolution of its digital copy from iPhone to Apple TV???

If it's showing up differently on two devices then that indicates an issue within iTunes. You would need to contact them so they would be able to look into what is causing the issue. It isn't something that a user on this forum can assist with.

Another user may have experienced something similar, but would not be able to give any further insight into why an issue occurred within iTunes. You would need to contact iTunes so they can look into it and then only they can give an explanation as to why it occurred.

You will need to contact iTunes.

I was saying another user won’t be able to personally offer any further insight. You are essentially waiting for the chance that not only someone else has experienced a similar issue but has contacted iTunes and is able to pass on information. This isn’t something that gets reported much so if you’d rather just wait around that is your choice. You would still have to ultimately contact iTunes so they can look into your issue.

I am very much paying attention to your responses and am stating the facts, which is to aid in a solution for your issue. Whether you choose to consider it helpful isn’t relevant. I will leave you to it.