The US embassy in Tehran used shredders too.
They used a linear shredder. Those don’t work to destroy docs. The Iranians pieced the strips together and used them to track down embassy employees. We know what happened then.
Cross cut shredders or chippers were invented to remedy that problem.
If the chicoms are doing this burning they are sending a message. There are better ways than burning. Lots of sabre rattling going on around the world right now.