iCloud Mail - push of the "read" status

[nihoso]

Hey, I am wondering why emails I read on one device, are not marked as read on my other devices automatically. Since I am using iCloud Mail which supports push, I expected it to be synced.
They are only marked as read, when I open the mail app on every device.

 

[fastbagger]

Because I think Apple thinks it uses too much battery. That is the one feature I want.