I'm pretty sure it isn't polyurethane foam. I'm not familiar with L200 foam. Plastazote is a brand name of polyolefin foam, and yeah, that's possible. It could also be polyethylene foam, which is commonly found in cheap camping pads and life jackets; though from the photos, I sorta doubt it.
Most of these foams have similar enough properties that they can all potentially work. If you're having trouble cutting it, you might just not have a sharp enough blade. A fresh blade on an X-acto knife, or disposable utility knife shouldn't have too much trouble cutting through it. You might just need to use multiple shallow strokes. Hot-wire tools of course just blast right through it.