BMX is not raced in laps. I followed it closely in the first half of the 90s, and on and off since then. I've never heard of laps in a BMX race. I've never even seen a BMX track that was designed for it. They race multiple heats in one day, but each one is still just a sprint to the end of the track.
This is ESPN, so they've either done something comeplety different than everybody else, or they got their terminology wrong. (again)