It seems to me that the degree of loyalty to the conciliar church (and especially the Second Vatican council) is the only criterion by which the Vatican allows or does not allow traditional liturgy. That is, if you sell your soul to the devil, he will allow you some traditional rites in return.

A phony war declared by guys who failed to notice that Rome had abandoned the Roman Rite over 50 years ago.
Fictions upon fictions of people unable to read with attention Quattuor abhinc annos - the mother of all "indultist" delusions. There they have been advised honestly and explicitly what is the "indult" system for.