Simple reason apple wants to save cost and make more profit. They chose to buy the screen that didn't include the aod support.
Your not making any factual sense.
1)
The custom apple oled display that Samsung display manufactures for apple according to apples specification is more expensive and has lower yield rates then the screens Samsung display sells to Samsung mobile.
2)
isn’t and a software feature? What does it have to do with hardware
Judging from your past posts I would sincerely doubt you would get an iPhone X’s or X’s max even if it did have Aod. So what’s your point again?