Why did I spin a main bearing?

Did you ever rev it while cold? I always thought that could spin a bearing. I have seen people in 3rd world countries do that routinely. They start, then rev it high in neutral for 30 sec, then race up and down the block. They seem to think that wakes up the engine's spirit or such. They also floor it as they shut off the motor, which hasn't been needed since the model T. Our problem is that after a new cam install, you are supposed to run >2000 rpm, which always bothered me on a cold engine.