I take it this is not normal oak plank flooring you can get at the
flooring stores (pic did not look like normal T&G boards, anyway).
Floorboards are normally nailed for this very reason, among others, but
there may have been a good reason to use screws here.

Regardless, I would first try to screw them all the way through. If
that didn't work, a Sawzall with a long bi-metal blade would most
likely eat it and ask for more. Small hole saw is the last option,
because fitting many special-made plugs won't be fun.

Good luck and tell us how you do,
H