As you said, this is all conjecture. But I think Rafa cares more about #1 than Roger does, if only because of
this. Further, his participation at the Paris Masters last year - where he secured the #1 ranking with one easy victory - implies that he does have it on his mind. Then he withdrew a couple rounds later with a knee injury....but f I remember correctly, he was a bit wobbly beforehand and many questioned his decision to play Paris. I think he clearly played to secure the ranking, which goes against what you are saying here.
The ranking is obviously not as important to them as Slams, but I think they're disingenuous if they claim they don't care at all.