That’s a feature. It lets your thumb scroll comfortably in a larger blank area so the content is always in view for you. There is no reason for things to be centered, it does not aid readability.
Not a feature on a 32inch ultrawide.
Use smaller window
Use phone horizontally.
Much more practically, the best designs are the ones who don't demand of the user they be consumed in a single form across every scenario.
Horizontal phones haven’t been practical for a while. The weight balance is off and you are forced to use it two handed. You’ll look like a toddler.
Just as impractical as expecting the user to use tiny windows on a 32" ultrawide. It's a literal example of "telling the user they are holding it wrong" being the wrong approach to the problems.
This only works on large enough tablets. On phones the page isn't readable without a 3x zoom.