On the subject of coaching of Children in interviews - due to their age a specialist interviewer usually has to speak to them in a certain way to extract relevant information.
A six year old is unlikely to know what cocaine is, and is unlikely to talk about a specific issue at request. Instead, they have to be drawn into conversations about these things. The difficulty from an evidentiary perspective is ensure that you don't lead the child towards a pre-determined conclusion. This is why specialists are used, these things are easy to fuck up.
If Nick isn't just babbling utter shite, entirely possible, he could just be objecting to how people normally interview children.