I don't think it'd necessarily need to be erotic as such, but the "show, don't tell" concept (a subset of "be specific") is, if not quite specific to fiction, at least a lot easier to screw up there. If you're writing about your lunch or your commute to work, you've already got a sense of the salient details and probably won't be tempted to hide behind coarse descriptions of your emotional state; neither's necessarily true if you're writing about some fictional character.