Think he means similar in usage rather than similar in meaning.
But yeah, you don’t use さん between friends – if you do, they’re going to wonder what they’ve done to offend you so much that you’re distancing yourself from them. For a different reason, you also don’t use it when talking about your own family members to other people.
The way it has been explained to me is that it is used to refer to someone outside your circle, so to speak, or those you are not close to. It always comes back to elevating others around you, that’s what the whole politeness thing is about. And more importantly, you don’t refer to yourself as さん to someone outside your circle because it would sound like you’re trying to elevate yourself above them and would thus be considered rude.
I vaguely remember something about not using suffixes when referring to someone inside one’s circle to someone on the outside of it (the ‘circle’ boundaries being defined by situation and context). Can anyone confirm and expand on this a bit?