If you require virtue >= x for entry into the Virtuous People's Club, this incentivizes demonstrations of virtue by people whose virtue level is approximately x, but may actually disincentivize demonstrations of virtue by people whose virtue level is substantially lower (because their performance will be compared against x).

For the club to confer a lot of prestige, x had better be substantially higher than most people's virtue level. Now, I suggest that (1) the unusually virtuous are probably already making some attempt to optimize for virtue, and optimizing for demonstrated virtue may actually make them functionally less virtuous; and (2) the great majority of people will be some way below x, so the existence of the VPC gives them no incentive to demonstrate virtue.