iPhone 11 display Zoom not working

Hi all

I recently upgraded to a iPhone 13 pro and while comparing with the wife’s iPhone 11 (not pro). She commented on how big my icons were on the screen. I said that’s because I have the display in ‘Zoom’ mode rather than standard. (Display settings, at the bottom).

I then went check her settings and she also had her iPhone in this setting however switching from standard to zoom (iPhone restarts) doesn’t do anything.

it’s on iOS 15.4.1. All fine.

1. Is this a know issue?
2. Is it because the iPhone 11 only has a LCD panel and can’t zoom the screen due to lower res display?
3. is there any other setting over ruling this?

very weird as if it was not available then it should be greyed out or missing in the options?

any help would be great.

(it’s not the zoom in screen by pinching it option)

cheers all.