Wow. Seems reasonable what they have done to get the product released under control. It is still Samsung who makes the Tensor G4, but the next chip they are trying to move to TSMC for even better performance.

WRT to GrapheneOS, most people who run it have much better battery and system performance.

AND, the software tech is the correct direction.

If we get the volume up, we can make our own open hardware Graphene phone, believe it. 

 Google designs the Tensor chips. Samsung is merely the foundry partner that manufacturers them for Google. Switching to TSMC is not a guarantee for better performance as the fundamental design is flawed. 
The Qualcomm snapdragon 8 gen3 is a superior chip that would better serve a GrapheneOS phone.  

 Do you design chips? 

 Did Siskel and Ebert write movies?