It does appear QF use a slightly different model #. Not necessarily too significant... it might just be a (slight) thrust rating increase, and can be reversed, or at least "points" to where the problem might lie. Or it's not relevant at all...
I pulled up Rolls pdf with a google search and for what it has to say is that there is a significant increase in take off thrust with a 5 minute limit on the 972 vs the 970. All the other numbers looked the same.
So with flex/assumed temp take offs not too sure how often they get into the range above the thrust of a 970 with a 972.
You may be on to something.
Not sure if there are any other internal differences in the engines. Maybe they are just pushing the limits of the design with the higher thrust rating.
VFD