I think Casselden was trying to draw a comparison to his interactions with Marion and JO, to try and get him to slip up while he was focused on JO.
I don't think it ended up coming off though? He said he once went to MB's house, which I think is consistent with his police statement?
Just more and more questions are raised though, like WHY would Marion want to store boxes of valuables at this guys house if they had such a limited period of interactions.
To me, it sounds more like the storage of her valuables at his house, is inline with the black tube that JO was told to store in her backyard for safe keeping while they were OS. ie. so he had access to them.