I had the same thought but just tested with a fairly standard "premium" plastic cube (not Rubick's brand) and I think it works in the same way. There are springs and that allows assembly/disassembly and I think it would work with a less flexible material. Not sure if the Rubick's brand ones are the same or if they really do rely on flexible plastic.
The original Rubiks brand cubes would rely on the springiness in the plastic. These tended to be rather hard to turn with even the slightest misalignment. Copy cats invented the improved mechanism. These will turn with a misalignment up to something silly like 40 degrees. Rubiks copied this mechanism for their own cubes eventually.
Long story short, a random chinese Rubiks cube knockoff is quite likely to be higher quality than an actual Rubiks brand cube these days.
