I've got a Maxpedition Condor and noticed the same thing. The hydration pocket, while pretty good-sized, has trouble fitting my Camelbak 70oz. Unbottle. It will however fit in the main body of the pack.

Wearing the pack with the Unbottle in the hydration pocket also gives me the feeling of having a waterbed on my back.

I think Maxpedition has come out with newer 2nd-generation packs of the Falcon and Condor, but I'm not sure if those have been adjusted for a better fit for the Camelbaks.