Yes, steel pipe to the knee will work equally well against all unlock methods. Graphene OS is supposed to be extra secure to better protect you against tools used by government agencies and law enforcement. It’s used by activists and such. IMHO using fingerprint on Graphene OS makes all this extra security meaningless because police can just force you to unlock and it will be legal:
techtimes.com/…/court-rules-thumbprint-phone-unlo…
Police would not be able to unlock this phone if the guy used pattern unlock.