I imagine that Spock, by the time he met Jim, was quite versed in ‘the bedroom arts’. He didn’t experience Pon Farr yet, but he weren’t no virgin.
Actually, since Uhura’s song in Charlie X I am under the impression, that he had acquired quite a reputation in that field, and he wasn’t ashamed of it neither. In fact, he seemed to like her singing that song. (Note also, that, according to Uhura female astronauts can’t wait to find out what he is like in bed. As in, isn’t there a female who knows already? :p)
And when T’Pring said, he was sort of a legend, I think that this reputation was what she meant (referring to both, him being mainly/only with men and being with them a lot).
And that, according to TMP Novelization, he considers human sex too mechanical (rubbing this and that part together), rational, logical - in comparison to vulcan love-making - tells us, that he must be of the more passionate kind, irrational and illogical in bed.
I really like this interpretation too. :3