That is an option, but IMO this is a bad way of policing a class or series. I dont know of another form of auto racing where the only time a technical rule is enforced, is when another competitor files a protest and deposit in order to have a class rule inspected & enforced. And this is more then just about engine displacement. This is the whole rules package.
This also causes animosity amongst the competitors. No one wants to be the bad guy or labeled a whiner. What if your protest is not upheld and you not only lose your $500 deposit, but now your competitors will think you are a whiner. Even if you win, many will think your just being a cry baby, because many rule infractions might not be performance or would have made them win that day, but its still a broken rule. Plus per the rules you have submit & file your written protest & deposit within 30 minutes of the time limit of the event. With Score you used to have to be in a $ paying position to be able to protest. I cant tell you how many times I have heard people say "so in so" is cheating or they suspect something, but no one wants to lay their money or name of the line for it. And really its not the competitors job to enforce the rules the Sanctioning body has written.
If you think about it, every other form of auto racing they have a pre-race inspection & a post-race inspection. Off Road Desert Racing does not seem to have any of that. The only inspection we have is for Safety and even that is questionable many times. Back in the day the Protest Option was a way to police the competitors while on a course where no one could see or monitor a whole off-road desert course.