I think the real point is, that although it may or may not have been necessary to be granted such an indult under the 1917 Code and/or other documents that were then in force, no indult is required now, since the law itself grants full power to bishops to permit Communion under both species.
It was the indult that changed what was then the GIRM.
The old GIRM had 19 different times when Communion under both species could be given. I’ve looked through the older sacramentaries, and there’s a definite progression where each printing contains more times when this is allowed. The latest version has 19 numbered items including “weekday Masses” then a paragraph saying “Sunday Masses” (so, 20 total).
It always read very strange to me. I often wondered to myself why bother? Why say that something is only permitted under certain circumstances, then conclude by saying, in effect, that this can be done anytime. It never quite made sense until I recently started to look at the history and noticed that the list just kept growing over the years. So that explains the long list. It was 4 then it was 10 then it was 20. All of these additions were a result of the US bishops conference asking for more adaptations. I have this memory that one version of the GIRM in a past Sacramentary even had the final time as “at any Mass.” Again, why bother with a list if the last item will only conclude with “anytime.”??
From what I can gather now, most of those permissions for adaptations have been either rescinded or not-renewed.
It seems to me that the Church is trying to send a message that both species should be reserved to special times. That’s the conclusion that certain bishops have arrived at, based on what we’ve already seen discussed here on these threads (and yes, I have checked the dioceses websites directly for confirmation).
The difference is that at the present time (at least until the new Missal is official), or perhaps until some time in the recent past, the new norms are that the bishop’s permission is required. That’s completely different from what we saw in the past where it could be done at any Mass at all, without even consulting with the bishop (granted, that he could still regulate it). I think that the Church is trying to tell the bishops not to give that permission too indiscriminately. Again, that seems to be the expressed opinion of a few bishops, so it’s not just wild speculation on my part.
In brief, in the past, it was up to the individual priest to do this on his own, based on the permission in the GIRM. Now however, the priest can only do it if the bishop specifically permits it. That’s the difference between then and now.