Ok, I have a lot of experience with this one. My last top had a lot of seersucker blocks, but not the tightly-woven stuff. This had bands of puckers alternating with woven stripes, and it stretched a LOT. From my test blocks, I learned it would indeed return to puckery when washed, but it also stretched out of shape when the puckers were pressed during construction, thereby making it hard to measure accurately.
What I did was to press seams manually with a plastic pressing tool (you could use anything) and try to keep the hot iron on the seam line. It also helped to shoot some steam onto the ironing board and then do the manual pressing on top of the warm cover.
i have yet to quilt this (hoping that the passage of time will dim the memories of its construction), but I definitely have a some fullness to quilt out.
That said, most other seersuckers are not so ornery, so I wouldn't reject them out of hand.
hugs,
Charlotte