Look. Unless you're a firm sedevacantist, the Church has the authority to change and even completely eliminate fasting regulations. So it's just consistent being consistent here with sedeplenism. If you believe that the V2 papal claimants are legitimate popes, then their fasting changes apply. Consequently, one would not be committing any sin by following the new regulations ... so it's only right to list them so that people can properly form their consciences. Even if one is merely in doubt about the legitimacy of the popes, then the binding nature of the old fasting laws is in doubt ... and therefore cannot bind consciences under the pain of sin.
So, if you believe that these men have been legitimate popes, you can't go around pretending that the old fasting laws remain in force under pain of sin. People would be following them by choice and in trying to keep the older spirit of the fast.
It's in cases like this that I see the R&R folks being inconsistent with themselves. Some of you assert that these men are indeed popes, but then howl and carry on as if the new fasting laws are not legitimate.