Isn't it relatively trivial to remove one of these by epoxying something to it or using a drill or dremel to modify it in some way (e.g. dremel a slot that a standard flathead can turn, or drill and use a screw remover)?

Or is the purpose less to prevent people from removing the screw and more tamper evidence?

Even in that case, with a photo or impression of the screw head, an unauthorized key/bit could be produced with with 3D printing (JLC3DP offers it cheap) or EDM.

If its on the wheel hub you’re going to need more than a dremel to do that, and you’re going to need something that breaks less than a flat head. There’s a reason they don’t make flat heads for impact drivers.

The button head is designed to be low profile and is rounded off enough to prevent tools from getting a good bite into it to cut a slot; on top of that they’ve designed these fasteners to torque super tight down (including ‘claw-like’ serrations on the bottom of the screwhwead) to basically require their tool so the bit doesn’t snap off if you try to make a duplicate.