Pchee, Miles' exact words when Michael gets on board: "your name isn't Kevin".

Even with the best of clairvoyants, medium-people or whatever is the name, it's not like he/she can read/know exactly, 100% etc. But considering what this and earlier episodes gave about Miles' gifts, fair to say that he's got the ability to communicate with the dead and read people's psychology (i.e. their hearts or minds, depending how one wishes to interpret that). If Miles had further conversation with 'Kevin' later (which this episode didn't show but it's not some remote possibility that they did) quite possible that Miles noticed/ read/ saw etc. that Kevin's related to this Benjamin Linus guy in some intriguing way.

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"Bear...? Is that you?"-- Hurley S03E4