I don't think this is a Graphene specific question/topic. However, you're going to use device A to connect to your cellular network and share internet access by WiFi to device B. From your providers perspective only device A is connected. Both devices share same IP assigned by the provider to device A because all traffic is routed through A. When browsing the web at device B, the webserver is still able to identify you e.g. by browser fingerprinting. So this adds no further security or privacy. You're just exposing the hardware identifiers of device A instead of B to your provider/government. No further benefit.
Furthermore you added another attack surface by sharing a WiFi which may be compromised or sniffed.