"This is also surprising. As a alumni admissions interviewer, we are instructed never to bring students into our homes. Please make sure you bring someone along with you (parent, etc). "
In the good old days when we applied in the 80s, I think all the interviews were in the homes of the alumni interviewer. You had to get the interview of course from a place like Princeton.
“Maybe the fact that I applied for one of their writing scholarships (did not get it) showed them some interest.”
If you’re really interested now in WashU, you can send a letter of continued interest, contact the adcom responsible for your region. Even though I’d lean to bio/spanish at UM LSA.