They've trimmed the bezels enough that the 13 Pro and 16 Pro are exactly the same width despite the bigger screen, and the 16 is only a few mm taller.
https://www.phonearena.com/phones/size/Apple-iPhone-13-Pro,A...
https://www.phonearena.com/phones/size/Apple-iPhone-13-Pro,A...
I understand it's not ideal, but I find it a valuable feature when I must operate one handed and sometimes struggle with the same issue.
I did also set up an accessibility feature where you can map a handful of actions to a double or triple tap on the back of the glass, and I mapped double-tap to trigger Reachability. But it's not super fast and overall a bit of a downgrade from the double capacitive TouchID tap on older models.