In a remodel we did some time ago... we extended a kitchen peninsula out on to a pergo floor, and nailed right thru it. According to the "Rep" at the lumber yard, the floating is for the exact reason described above, expansion and contraction. In the little amount of sqare footage that was actullay secured to the floor, that floating
was not an issue. The design was for large areas not to expand and buckle within the walls. And the no nail- pergo design
is for cosmetic reasons (people did not want to see nail heads. So, I am pretty sure, a wall or two or four, at an average of two feet long + or - , will not buckle your Pergo. This is only information shared as heard from the "Rep". But, after more than 5 yrs, the floor we dealt with is doin great!