Good point but I am not locking up for all day in Oakland. Just for a few hours on the N Shore trail while I swim.
Apparently you can break the lock with a screwdriver. But it is a deterrent. Just like when I use a thin cable lock for my road bike when I run in places. I wouldn’t leave it all day like that, but hopefully it’s better than nothing.
If you just want a deterrent, throw a luggage lock (or padlock if it’ll fit) onto a gym bag/backpack and lock that to your U-lock. Not knife proof, but it’ll deter casual theft. Drag the bag around in the mud a while & nobody will be interested in it.
The one on gun safes is very interesting. In fact, even though he defeats them easily, some of those smaller safes might actually be practical for bicycle storage, if they could be secured to the frame. Certainly better than this plastic thing. (Especially if you’re willing to do a bit of hacking, as he talks about.)