Mine was straight out of the box too, I got it with my 2017 iMac 5K purchase in July. But after a few months the bending happened over time. I would suggest waiting some confirmation if a new batch/revision is in place before hassling for a replacement unit.
i thought people were getting bent keyboards straight out of the box? i honestly cant say about mine, since i didnt notice it right away. i know it never sat right on my table, but i dismissed it at first because my table is rustic and not perfectly flat.
putting a little felt pat in the middle isnt a bad idea. would make the keyboard less bouncy as well.