Yes I am absolutely sure. I can see it while leveling the bed (using a feeler gauge). If I have the correct distance between nozzle and bed on the edges the nozzle scratches in the middle. And if perfect in the middle the edges are to far away. When I start a test print I can even see the filament not being squished enough to the bed on the sides while perfect in the middle. Warping only occurs to me when printing PETG and even then only slightly and on longer prints.