IMHO, this is consistent with the memory he related to police. On another thread we've discussed whether or not he is remembering the 16th specifically or another day altogether, the 9th or the 13th being the most likely candidates in my mind. KC and Caylee did not leave before 4PM, as we have determined. I think it is likely he either did not see her on the 16th or saw very little of her, which is why another day sticks in his mind and he is mapping it onto the 16th.
I see no issue with him unconsciously doing this. It had been five weeks since he'd seen Caylee, and the memory he calls up is the one that is most complete, and he feels it must be the right one. Over time, perhaps more "detail" has come in as he thinks about times he's woken with Caylee, had breakfast, and watched Sponge Bob. But I don't think there is anything nefarious going on.