What did your friend think was odd? Writing a TY note for the interview or the wording itself?
It's pretty common to write TY notes for an interview. In my experience, about 25-50% of candidates I've interviewd do. Once a candidate for a position I was interviewing sat just ourside our office (in the lobby) and wrote out her notes, then asked an admin to deliver them to our desks. Often I get a thank you email.
For me, as an interviewer, it wouldn't really make any difference whether I got that note or not, so I don't know if they really help. But heck, they don't hurt!