Nobody is going to steal a Sheldon-locked bike by cutting the wheel, ever. At that point, it's easier to cut the signpost it's locked to, and I'm not joking.
Cutting the top tube is definitely *a lot easier* than cutting the wheel, tyre and all. Somebody dig up the vid where a frambuilder chops a frame in half to install that take-apart travel joint thigy (WTF is it called?)

The reason why I think Sheldon-locking is very silly most of the time is that some dumb-ass thief might *try* to steal the frame and damage your ****. Also, the lock will usually easily reach around the chainstay, seatstay or seattube as well as the rim, so why not reassure the crooks that the bike *is* locked?