This is a potentially slow operation if an user has millions of ruptures. So we are slowing down the upgrade process for all users, even if the fix only applies to users that need the GMF-on-the-fly feature (i.e. nobody since it was not in 1.0). And if we do set the tag to be equal to the id, then there will be an ordering on the old hazard computations, but an ordering inconsistent with the new code, i.e. repeating the hazard computation will extract the ruptures in a different order than before. So I do not see an advantage in doing so. It is equally inconsistent to leave the tag for old ruptures to NULL and it is faster and somewhat cleaner.