I think that the appearance of 'bending' is due to the 4 clips on the bottom cover that hook (or slide) onto catches. If you look closely or at an angle you can see where the clips are sort of pulling the bottom cover down slightly and keeping it firmly in place.
This feels like an over-designed way of securing the bottom cover (making the removal and replacement unnecessarily difficult), when they could have just used one or two more screws, but this is what they decided to do.
I am sure with most units, the bottom cover opening has very slight 'waves' and you'd have to look at an extreme angle to even notice. From normal views, it should look even and straight.
The OP's situation appears to be a poorly fitted bottom cover from the factory where one of the clips didn't catch at all, and is sitting on top of the catch, causing a more pronounced bulge.
Another thing I noticed about the bottom cover on the M2 Air is that there are more prominent seams along the edges - the cover doesn't sit flush on all units. I found this by just picking up the display models at the Apple Store - I felt the seams immediately while handling them and decided to check all display units out.
This varies from unit to unit (and is more noticeable by the corner screws) so this must be due to very slight variances in the bottom cover size. Some sit perfectly flush where you cannot feel the seams at all (normal), while some are seated a hair too low, and others sit a hair too high. I also noticed that this only affected one or two sides in other models.
The M1 Air has a better fit and finish when it comes to the bottom cover (and better sounding speakers I might add). But, the M2 in all other areas has a superior design and feel (in my opinion).