I wonder if they had both been asked about the sound the sliding door makes when they had spoken with LE/search organizers/whomever talked to them about it before. I can see where, if you are telling someone your account of what had happened and they ask clarifying questions that make you realize that some details (e.g., the sliding door is quiet and that's why they were unable to hear it open or close) are relevant to your story, then you make sure to include those details in your subsequent retellings of the story either for the purpose of making sure your story is clear for the listener, or you think it adds more credibility to your story. Whether the story is true or not, and whether you were initially interviewed together or separately...like, if [that person] was wondering about [that detail], I should make sure [these people] are aware of [that detail] as well, so they don't have to ask about it.
I hope that makes a bit of sense to anyone, it was hard to type out what I was thinking.