Stranger called me beautiful? Opinion?

Anonymous
I'm an English teacher and I was teaching the verb 'to be' to this very dashing young man. I was going through it with him and getting him to repeat after me, and after I said "you are" he said "you are beautiful" to me. Of course, it was flattering and it did take me by surprise. Are compliments like this given by strangers, a man I had met not less than an hour ago, genuine? What was he thinking? As a guy, would you only say things like this to a woman, let alone a stranger, if you really felt it?
Stranger called me beautiful? Opinion?
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