That XKCD comic was wrong and one of the rare truly stupid and actively misinformative ones. Security measures are always about responding to threat scenarios and economics, and must in turn be analyzed in context. The general use paradigm for an average device involves many different threats and in turn separate measures for each one. FDE for example is only about protecting from cold attacks, warm/hot ones are just plain out of scope.

Similarly, authentication systems (including passcodes and biometrics) are purely about ensuring that only authorized people may gain access with whatever permissions they're authorized for and no more. Their threat scenario and usage does not involve intent. Authentication "primitives" can be used as part of a counter-intent security measure, but by themselves they only determine a "who" not a "why". Strong authentication backed by strong encryption is a stand alone good and a required foundation to do more complex stuff, but that's it. The "wrench" attack is an intent-based threat scenario: the person performing access is in fact authorized, and there is nothing at all buggy, malfunctioning, misdesigned, weak or wrong in any way with an authentication system allowing access. It'd take an intent reactive security measure to deal with.

Regrettably there are still no main stream smartphones that implement this as far as I know (though at times it's been possible to do your own to some extent via jailbreaking on iDevices at least and I assume on rooted Android as well). Which is really too bad because Apple in particular have a lot of very good tools at this point to do a really, really good implementation. A classic measure would be coercion/distress codes, ie., alternate passcodes an operator can enter that will cause the device to perform different actions then a straight authentication (these can range from a full deletion to more subtle actions like a silent alarm). Apple though could use TouchID/FaceID to make this even more user friendly, merely "use this finger vs that finger" or "be making this facial expression vs that one" as triggers. They (and anyone else with a secure hardware stack) could also implement temporal and spatial trigger options which would be very useful. Finally the iOS design is decently placed to allow relatively easy and more selective view filters on accessing apps and data due to how heavily everything is silo'd. The silos have been intensely frustrating a lot of the time vs standard computer access patterns, but in this instance it could be a real strength. Imagine being able to have a "travel view" we could set before a trip so that sensitive apps simply vanish until GPS indicates we've arrived at our destination or connected to a specific network or whatever. Or there could be distress views that react to a facial expression or code or finger and then permanently hide everything but a cleaned minimal data and app set, including your cloud stuff, until you get home and enter a special unlock code (or for a set amount of time or whatever).

I think intent-systems/view triggers will (or at least should) be the next big leap forward for helping our personal information devices get not just more secure and better for privacy but more productive. I'd like to see that start to show up in future versions of iOS and Android more then nearly anything else.