That suspect's iPhone 5C had a weak numeric passcode, so the only defense was hardware security limiting the number of attempts. Someone reverse-engineered that, wasn't a backdoor. I'm not sure how GrapheneOS differs from regular Android or iPhone on hardware security, but seems like it's basically the same. Need a secure passphrase to be truly safe.
I didn't say it was a backdoor. GrapheneOS is the only OS that consistently shows as unhackable on lists of devices vendors can hack for police. Which could make it a honeypot, but anything could be one.
