Are bike computer magnets all the same?

The only differences are how they are designed to attach to the spoke.  I have some that will only fit on a rounded spoke (which is a PITA since my new bike has bladed spokes), some that you can attach without a screwdriver. My riding buddy has one on his old bike that is not a round button, but elongated like the spoke it sits on.

But you could use any magnet.  Heck, I bet you could zip-tie a refrigator magnet on the spoke and get a reading. I always save the magnets when I have a computer die.  It paid off recently when I picked up a returned wireless cyclometer at REI for under $5 because it did not have the magnet!

This seems odd to me.  A magnet is a magnet.  I did find an article in Sheldon Brown about how the orientation of the magnet on the wheel might affect the readings, so I could imagine if the magnet is oriented oddly it would have some impact, but hard to imagine it not working at all.