Portrait / landscape marked up images are delivered in different resolutions

1. What is the problem? Be very detailed.
Marked up images taken in landscape orientation are delivered in a different resolution to portrait, landscape images lose some detail vs portrait.

Portrait: 1600x2134 (~3.4MP) : Maxed out 1600px wide = screen dimension as soft buttons display on short side of screen
Landscape: 1990x1492 (~2.9MP) : Resized from 1600px tall to 1492px tall due to soft buttons taking up 108px on long side of screen

2. What app or server are you using and on what device and operating system? Include version numbers.

Samsung Galaxy Tab S6 SM-T865 (screen res 2560x1600, camera set to 4:3 aspect)
Collect 2021.3.4

3. What you have you tried to fix the problem?
I checked this before I twigged to the reason why, not relevant.
Check device screen resolution isn't lowered - OK, can't change
max-pixels is 2560, and non marked up images are 2560px long, OK
Screen shot on misbehaving tablet was 2560x1600 - OK
Photo taken in camera app was 4128x3096 - OK
Camera settings are OK, 4:3, non HEIF, no option to change resolution
Project settings \ Form Management \ Image Size : Original size from camera - OK

4. What steps can we take to reproduce the problem?

Create a form with an image widget with annotate, annotate a portrait and also a landscape image, ensure max-pixels is >screen resolution, compare delivered image dimensions.

Observe when marking up that app switch/home/back soft buttons sit in different areas for portrait and landscape markup and reduce the 'screenshot' area for a landscape marked up image if the captured image has a squatter aspect than the screen, opposite problem for portrait images and captured image aspect taller than screen resolution.

For my 4:3 camera aspect setting, for a portrait image the soft buttons sit on unused grey area, as the image is squatter than the screen aspect so it's letterboxed.

But for landscape images the 4:3 image is now pillarboxed (grey areas are still along the short edges), so the soft buttons rendered on the long edge don't allow the image to maximise its vertical height.