GrapheneOS duress PIN could land a man in prison

If he hadn't given the authorities the duress pin, and presumably they had seized it, would the encryption/protection GrapheneOS provides have been enough to keep them from accessing it's contents? I've never used Graphene so I'm unfamiliar with all it's features.

My Samsung phone has a feature to automatically format the device if the wrong code is entered X number of times, and I have security software that would let me wipe it remotely (if it still had internet access) so this whole situation brings up a lot of questions about features like this.

EDIT More discussion about it here, but it's quite technical. I was a bit confused about the rate limiting stuff and etc.

GrapheneOS protections against data extraction from locked devices - HN Post https://news.ycombinator.com/item?id=49055169