Those 'some' would be misinformed. Soft plywood will bend. There are other soft plywoods that will snap only because they don't employ cross-lamination.
Hard Plywood will not bend or snap in half because of its material composition and construction. Each 'ply' or layer is cross-laminated to the other. This is deliberately done to prevent all the layers aligning their grain to one another. If each ply layers grain aligned with the one above/below that would allow for bending or warping. Plywood is very strong. I have a 3/4" thick sheet of hard plywood under my matress for extra support and in 10 years, with 2 people sleeping on it, it remains as straight as the day I put it there. Ny back is still crooked, by the plywood is still straight.
One excellent example of hard plywood application is in a Yamaha piano pinblock. Cross-laminated hard plywood holds the string tension, about 20 tons of it, and can reliably perform for 100 years.