The problems with Spinn go back to the fabric manufacturer. The particular spinnaker fabric that is used for tarps is a little different than silnylon in that not only is it polyester based instead of nylon, but the waterproof aspect comes from a PU coating on the surface rather than silicone impregnation. That's part of why it was _more_ waterproof than Sil. The quality of the PU coating was inconsistent, as stated by several manufacturers, so they stopped using it.
It's worth noting that different vendors source their fabrics from varying supply chains, though. JRB may very well have sourced theirs before the issues, or from batches without any issue.
JRB is a long-running quality business that backs up their products. I wouldn't be concerned.
I still think spinn is one of the best all round fabric choices for waterproofness vs weight vs price.