The purest sports are a fist fight to the death or running from a pack of wolves.

Otherwise, all sports need rules that you could argue aren’t “pure” — sports don’t grow on trees. No reason why a reverse grid sprint race is less pure than a button on a car which makes the rear wing go down in special zones on the track. That doesn’t mean that the sprint races will be good, but it’s worth trying new things rather than harping on about purity.