Yes, just like any lumber, you should ideally always sticker your pressure-treated lumber and let it acclimate for a couple weeks before using it to let it dry out and acclimate to your environment.
Wood moves as it absorbs or releases moisture, even the moisture injected into it during the pressure-treating process. All you need to do for proof is to look at the picnic tables sitting outside your local home improvement center about halfway through the end of the summer. After they are assembled and set outside for display, they are always warped and one leg is several inches high up off the ground.