The Boss people were quick to get back to me, and I will just post their reply in full.
Hey Brent,
That plastic hull load has a pressure of 10,500psi and our Fiber wad hulls have a pressure of 8500psi.
We dont have the Fiber wad shell on our website, but did make this as a lower pressure load than our standard load for the low pressure guys out there.
What pressure do you need or want to hit?
Thanks,
Zach
Thanks for posting that, Brent. It piqued my interest enough that I emailed them to get further info, and pricing, on the 8500 psi loads. They sent an automated reply back saying that they're overwhelmed with requests for information and it might be a few days before I receive a personal reply.

Sounds like a load I would be very interested in. I asked if they are in paper hulls, as well as having fiber wads, because of the extreme reduction in pressure (a 2000 psi drop). It will be interesting to hear back from them.
Best, SRH