I don't see an issue for this already, which supprises me since this seems pretty major and fixable.
When the iPhone is horizontal, it doesnt take the full width of the display. This is particularly noticable in light mode due to the large bar caused by the dynamic island.
Additionally, it doesnt feel like the horizontal view is properly scaled either. It's almost as if it's cropping the portrait rather than actually using a larger width. This is most noticable with text, as in safari, it's much smaller.
Orion:

Safari:

This may not be the best example because the video player does have padding on either side, so you could mistake Safari for also having this issue, but it's apparent with other sites. But it also shows how the scaling is not quite right either, the player is much larger than in Safari —as well as the text.
There should be no bars and the width should be the entire screen width, not just the viewport with safe zones.
I also mentioned this issue here
1.3.31 (4) (WebKit 8622.2.11.10.8)
26