I'm kind of disturbed and hugely suspicious whenever Catholics many decades before Vatican II and the entire history of the Trad movement (1969 - 2023 the present day) were allegedly wrong about something.
I mean, at this point, the "regular" O My Jesus prayer is TRADITIONAL, even if it doesn't mention Purgatory, even if Masons conspired to suppress that line. Think of how divisive it would be to try to correct it now. We wouldn't be able to say Rosaries together! A good portion of people would, for good reason, stick with the "traditional" version of the prayer, while others -- the doctrinal purists -- would switch to the new one, come what may. And what would come, in my opinion, would be needless division and fighting. And the devil would be laughing his burning red ass off the whole time.
Much more evil would come of it, than the microscopic good done by professing belief in purgatory in this particular prayer. Guess what? Trads already believe in Purgatory. We're not Novus Ordo. There's no falling-away from belief in Purgatory in the Trad world. Purgatory doesn't have to be literally EVERYWHERE in EVERY SINGLE PRAYER for us to keep believing in it. As long as it has a decent presence overall, the Faithful will continue to believe in it. Our priests preach it. Our traditional practices reinforce it. Our Traditional artwork teaches it. Our Mass mentions it. We still celebrate November as the Month of the Holy Souls and Trads do plenty of things to celebrate that month properly. Etc.
Do I need to remind some that we Trads still celebrate Requiem Masses with black vestments? The whole TRADITIONAL MASS for the faithful departed assumes they're in Purgatory -- not heaven. We don't eulogize or canonize the deceased, as they do in the Novus Ordo with their white vestments. So again, it's just not an issue in the Trad world.
This new version of the prayer is a solution in search of a problem.
The fact is, God has allowed us all to learn the "imperfect" version -- so it must be His will. I would say it's TOO LATE to go back and fix it now. We have 105 years of Tradition, of habit, of precedent, that would have to be undone and wiped out. The Church doesn't work that way. Things with "venerable usage" get preserved.