Sure, it’s possible that China deployed a completely novel type of weather balloon. But if so, it should not be surprised by the interception of its unusual balloon when it entered US airspace.
For that matter, if you designed a brand new weather instrument that was carried in the back of a Cessna, and then you flew that Cessna into Chinese airspace to carry out your measurements, then you should expect to be intercepted and probably arrested. After all, Mathias Rust was sentenced to four years for violating Soviet airspace.