What is the explanation of the talmudic dictum (Sanhedrin 62b, Kreisos 19b) that one who inadvertently sins in the areas of forbidden foods or sexual relations (e.g. reaches for kosher food, misses it and instead puts non-kosher in his mouth) must bring a korban chatas because "he received pleasure" even though other sins would be exempt from a korban in this case? What characteristic do these sins share that gives them a this unique legal status? How are these sins different from e.g. shatnez which seems to also dependent on pleasure (see Yevamos 4b)?
Some Acharonim (e.g. R. Elchonon Wasserman in Kovetz Shiurim) explain that the prohibition is actually the pleasure itself, not the act, so the disconnect from the act through lack of intent doesn't exempt them. I wondered if Rishonim hold of this or perhaps have some chiddush about korban chatas, or perhaps a different explanation.