This uses a TEE (a chip that is hard to take apart contain a private key provided by Intel), so the privacy system is very boring (they think the person who owns the TEE will not be able to see what the chip is doing).
It's odd to design a secure system and write a paper, when the security is based on something like TEE. There's tons of literature on breaking TEEs. I can't imagine anyone doing other than checkbox compliance with that level of security.
However, that doesn’t mean TEE don’t provide a meaningful level of security, especially when combined with Shamir sharing between enclaves. Few actors will be able to compromise 100 TEEs distributed across the world and made by different vendors.
And just like cryptography, TEEs are getting better with every release, and will soon be very, very hard to break.