It's really no more than a matter of semantics, Any interval mod-7 gives you the number of the scale degree on which the interval lands within the current octav

It's really no more than a matter of semantics, Any interval mod-7 gives you the number of the scale degree on which the interval lands within the current octave. This doesn't change if with zero-indexing. A Major 10th mod-7 is a Major 3rd regardless of zero or one-based indexing, the only difference is which notes in the current key you're actually talking about (in the key of C it would be E or D for one-based and zero-based indexing respectively) I don't know that it's any easier to remember "the tonic is 0" than it is to remember "the tonic is 1"