That's why it is weird. He was being asked about what happened that morning, but instead he alluded to what generally tended to happen rather than answer the question in a way which would have confirmed what was shown in the cctv footage. It was the one thing that jarred with me although I also thought it odd that he twice mentioned changing into gym clothes and possibly odd to even change at all given that he was keen to get down to look for NB at the river. JMO. These niggles did not stop me from feeling a lot of sympathy for him and I presumed they were just because he was rightly feeling nervous and distressed.
(in my own words)
Yes, under what must be immense stress, he had described at the start a little of why that morning had been somehow different from usual, under the circumstances it's possible he wasn't able, or did not, relate every single reason. He did describe a typical morning as opposed to that morning, and who normally did what, and he did not say whether he or NB loaded the car that morning, but he had already said it was different and seemed more organised (all under immense stress IMO and in front of the cameras for broadcast).
He might have loaded the car himself and NB opened the boot at some stage? I don't think he was attempting to match his words with the doorbell photos. Also, perhaps one of that mornings 'differences' was that he didn't need to load the car because NB did that herself ?
I don't think him changing into gym clothes is odd (and also he has a way of repeating some statements), he expresses being concerned, and, getting no answers to 3 attempts to phone her, he was about to go and find NB before going to the gym, he was in a state of mind that she was somehow held up (only by about half an hour note) but he was going to go and find her, he expected he would meet her along the way, and possibly, in his wildest dreams had no concept of her as a missing person at that point. Then at that point, having already changed into his gym gear and just leaving, he was phoned by the school and told the dog and phone had been found but not NB, he left and phoned the police on his way to the river.
He did not seem to me to be a well-rehearsed performer with a practiced script, but someone recalling what he could and finding the words to express it as best he could and trying to get it right.