Well I would say if it says "No Fur or Leather" I would do it.
I put some otter and bobcats in my freezer last year in nothing, just threw them in there and pulled them out a month ago and shipped them to Moyle, they all looked good.
If you have fur and can get them in a freezer bag and vacuum them, try it. But don't use those space bags for the reason they say.
JC