I don’t really buy it. Not as “it didn’t happen” but as in, “context is wrong.”
First off, at many schools, the informational interviews are done by students and recent grads.
That’s why they are called informational and not evaluative. This isn’t like the BS process – it’s far less personal. These “interviewers” will have no impact on admissions. Their “job” is to know something about their school, not your high school. Sounds like you got someone who’s really off script! I could relay a few nutty convos we had at a number of colleges with kids who had admissions gigs. It’s one of the many reasons there is such serendipity in how a visit unfolds. But I would not give this another moment of thought.
The AO will know your school and if there is any doubt that it’s not the case, have the DA CC reach out. BS kids are dialed into selective colleges so it seems unlikely that DA will be an unknown to the app reader (who will be reading apps from MA.)
If this was a school that interested you, your chances are not being hurt by coming from DA. (And it doesn’t sound like you’ll have any competition from other DA classmates, because, wow – your kid has to be the best one applying!)