No matter what classification is used, there will be variations. However, using a deterministic criteria reduces incentive to game the system. More importantl

No matter what classification is used, there will be variations. However, using a deterministic criteria reduces incentive to game the system. More importantly, it reduces (for example) the pressure on participants to change their sexual identity to improve their competition level in a sport or at the least give the impression that the change was made for competitive reasons.