Nat Friedman, who I believe commissioned this site, said he was surprised at this finding: https://x.com/natfriedman/status/1872836471398539379

Direct link to a paper in replies if you don't use X: https://www.researchgate.net/publication/286203208_Effect_of...

Microwaving causes individual particles to join into a delicious plastic-cheese emulsion, making them undetectable.

I figure it made the plastic less detectable by whatever measurement method was used.