I'm installing Bruce hardwood floor (5/16" x 2 1/4" solid oak) and
noticed that many strips are warped out of the box, although they've
been opened in the same room where they'll be installed for a few days.
The longer ones leave a gap up to 3/4" below them, although the floor
is required to be level within 1/8" over 10'.

It seems that as I'll be nailing them down upstairs, the warpage is
still manageable. However, I'll be gluing the same strips down on
concrete downstairs, when the warpage gets me concerned, for the glue
doesn't have much holding power until cured.

Is it normal or did I get a bad batch?

TIA