Yup, lots of bmx racers can sprint a lot better than generic roadies. All about that hole-shot.
If it's actually 1/8th or a 1/4... push for it to be the 1/4....your buddy is toast if you aren't a total Fred. That's simply too far for a bmx bike's gearing to work out.
An 1/8 mile is 300 meters. So, you may be toast if it is 1/8 mile or less.
Video please. Results please, with data. Give your boy a spare gps to throw in his pocket also.
Also, consider a double-nothing bet on swapping bikes for a second race. If you trust each other and have similar shoe sizes.