For someone who doens’t care, you were awfully insistent that there is no way that we can know. On the contrary, it’s incredibly easy to know.
Yes, JP2 was attended by a specialist on that one occasion - because on that one occasion he needed care that was beyond the capabilities of his own physician to provide. It’s called an emergency.
And if Benedict were dying, and desperately in need of confession for that reason, doubtless he would employ the services of any priest who was handy. Otherwise there is no need.
As I said before, the man is hand-picked by His Holiness for the job. Rest assured then that he does it! No point appointing him otherwise.
And a Pope wants multiple priests to confess to, he surely can and doubtless will appoint multiple confessors. Why not?
In either case, we KNOW who he confesses to. To repeat, maybe if he were in the middle of nowhere and/or in danger of death he would confess to someone else, but Benedict has not been in that position during his time as Pope.