Graphene OS provides advanced security capabilities and a thorough defense-in-depth approach including a hardened supply chain. GOS aims to provide mechanisms to protect against 0day attacks. For example Celebrite can not open up GOS. GOS relys on hardware support provided by Pixels. Graphene OS works on getting their developments upstream.
For a list of security features see here [0].
[0] https://grapheneos.org/features