There is a major difference between personalization and "pure" relevance, at least as used here. However, it is more of a question of inputs than actual terms.
"Pure" relevance is solely a function of the query and the document - R(q,d).
Personalization involves the user and possibly the context - R(q,d,u,x). Now, if you consider the user and their context to be part of the query, then yes, it's the same thing as relevance.
So the real question: should the user's identity/history/profile and/or current context be considered a part of the relevance function or not? DDG says no, Google says yes.
Thinking of it in this way makes the real question clearer. Unfortunately, it will probably make little sense to most Real Users.
"Pure" relevance is solely a function of the query and the document - R(q,d).
Personalization involves the user and possibly the context - R(q,d,u,x). Now, if you consider the user and their context to be part of the query, then yes, it's the same thing as relevance.
So the real question: should the user's identity/history/profile and/or current context be considered a part of the relevance function or not? DDG says no, Google says yes.
Thinking of it in this way makes the real question clearer. Unfortunately, it will probably make little sense to most Real Users.