People who have been asserting something as firmly as we have seen Morgan assert Harry isn't innocent recanting on their deathbed to a more sympathetic position is neither convincingly realistic nor a trope I am fond of; and this holds whether Morgan genuinely believes Harry is guilty or not. Either way it didn't ring true to me.
It was not at his dead bed, it was at the beginning of the book. It was clear that they both got a better understanding of each other during the years and that understanding was won the hard way, not with a sudden soul gaze or so. Morgans understanding of Harry at the beginning of Turn Coat was already enough for him to go to Chicago of all places. The hardest thing for both actually is to acknowledge it. Dying might make that easier, I don't know.
But Harry's understanding had grown too. These were not the same people that wanted to kill each other in Summer Knight.
I don't like dead bed confessions or conversions either but this was neither of these, he just discussed his actions and said some things Harry needed to know.