I've actually kind of wanted something like that.
Sometimes there is no size setting that will get the text lines on a page to fit horizontally without making the text too small to read. Making it large enough to read means lots of left and right scrolling which is annoying.
A mode where moving the phone sideways scrolls the text at a matching rate so that the experience is similar to reading a page with a magnifying glass might be handy.
Most people would rather lines to be broken up and wrapped around than to have to walk around the room to read. Do you often find yourself reading photographs of stone tables or something?
Why would you have to walk? You would be moving the phone back and forth by less than the width of a page.
Wrapping is fine on some material, but when there are tables it can be very annoying.