This "novel" feature is already supported by GrapheneOS and set to trigger after 18 hours by default, with the option for the user to adjust it to their preference. There is no good reason to force the choice of 72 hours on everybody. That's a user-hostile design decision.
How is Graphene working for you?
Not OP. But I am using GrapheneOS for almost 4 months now. It is a breath of fresh air. Network Permission, Contact Scope, Duress PIN, Hardened Malloc, JIT tuning, Sandboxed Google Play etc.. are some key privacy and security features in Graphene. Will never go back to Apple's or Google's surveillance platforms.