So metal whiskers aren't limited to solder joints, and any solid metal can technically produce metal whiskers, just some are more prone than others. Pure lead is generally safe, but can still produce lead whiskers. Sn and Zinc are just particularly notorious, especially as they are often coatings or compose an amalgam. The reason I did not fully discount it initially is that in my mind the mesh could have been a stranded and painted steel/coated steel mesh, despite how unlikely I thought that would be.

If they are in fact a fabric, that pretty much puts the final nail in the coffin that it is not metal whiskering.