Aren't there any RAC air racers on PPRune to defend their chosen hobby? It does seem a bit bizarre to me as well but there must be something to it. Is it like amateur motor racing where they're always fiddling with their engines to get the last ounce of performance? Smoothing out the airframe to reduce drag etc.?
I know they've always had handicapping though as watched an old Pathe newsreel the other day with a civvy Hurricane winning the Kings Cup just after the war. He had to start the race long after the others had taken off!