Funnily, at 7.6" (unfolded) it's less than an inch bigger than a Pixel 7a Pro (6.7"). Why go through this rigmarole of folding when you're barely adding much realestate?
An inch in aspect ratio is a relatively large change, considering it entails ~70% of an inch in both dimensions. It would be better to compare screen area or vertical and horizontal dimensions separately, to get a clear picture of the difference.
The Pixel 7 Pro body is 162.9 x 76.6 mm, giving it an area of 12,478 mm^2. The Pixel Fold body is 139.7 x 158.7 mm, giving it an area of 22,170 mm^2. So the area of the folding phone is almost twice the size! This was surprising to me since, as you say, the diagonal lengths are similar. Of course, it's due to the Fold having a more square shape.
Caveat: this is measuring the size of the phone itself, not the screens, since that was easier to find.
I guess that's why I'm not a VP at some BigCo.