Yea I have some in 17x22 sheets that has gone unused. It's curling even in the box. My experience is all of these alpha cellulose gloss fiber papers curl like that and that also causes scratches in printing, especially in roll form. Platine is cotton and like Hahnemuhle cotton gloss papers such as Photorag Baryta, remain flat in portfolios.
A tip, if you want to flatten Platine from rolls quickly just use a hair drier and you won't need a dry mount press.
I have printed a little bit with the Canson Baryta Prestige. It is a very heavy paper with a fair amount of curl. I personally didn't like the more shimmery, lustre surface. If you have tested the Canson Lustre vs the PhotoSatin papers that is similar to the difference between the Baryta Prestige vs. Platine. Naturally, it is mostly a matter of taste but I simply didn't like the surface as well and the roll I purchased has gone unused.
FWIW.