Another tradeoff GrapheneOS makes is because of the way they configure the USB port makes it more possible that you will irreversibly brick your phone by accident. You could say that the USB management is the only really material difference between Android and GrapheneOS when it comes to a law enforcement search threat model, but that also comes with a tradeoff.
Good point about the USB thing btw. It's obvious to me and the reason why I go one step further and leave USB debugging always enabled now that there's this private key authorisation method anyway (it asks for computers whose key it doesn't yet trust), but indeed a lot of users might follow GrapheneOS' advice without realising