Googling the interviewer, or interviewee, is specifically banned by my alma mater. The student should not google the person offering to interview them, and the interviewer agrees not to google the student.
I have NEVER heard that “most” American PhDs do not identify themselves as doctor. Most I have dealt with both in industry and academia DO in professional settings, and an alumni interview is considered professional not casual. Perhaps y’all run in different circles than I do.
The exceptions are obviously social (barring the most formal social events) where your first name would be appropriate (“Mary and John Jones”, not “Dr. Mary and John Jones” because no one is being called “Mr.” or “Mrs.” either) and businesses where being “Dr. Jones” would be looked upon as snobbish by clients and/or co-workers. Of course you’d call your co-worker “Mary” if you got to know her, but initially, “Dr. Jones” would be appropriate, especially if you are a subordinate.
My answer would be yes, it is stalker-like, so do NOT mention it, and some colleges specifically ban it. Alumni interviewers also do not get the student’s application to review at my alma mater, so it’s not like they know you any more than your name, your intended major if any, and and intended college of matriculation. As well as brief contact info.
As a college professor, I feel that too many students are lax about using proper titles. When you enter a four-year college, expect all professors are to be called “Dr.” whatever unless told otherwise.
In this case, the interviewer did not offer up degrees, so best to say “Good morning” or something without a name. I also tend to leave a student’s name out of emails, because very often I get the official name, whether working or doing an alumni interview, and I have no idea what they really would want to be called.
Also he may not have wanted you to know that he did not attend Harvard as an undergrad. Don’t ask him about Stanford vs. Harvard by the way, and he shouldn’t be mentioning Stanford nor interviewing for them this application cycle.