They should instead be within a Specials/Season 0. While BBC iPlayer does list them as part of the Seasons 2 and 3, they tend not to put a "Specials" list at all, hence they do their next best based on the air dates and closest season.

They also don't get everything particularly correct like Season 2 Episode 5 being named "Father's Class" when it is originally titled "Father's Clinic", my source for that would be basically every single other source you could find, including some Sky services like NOW, BritBox, and the like.

The Wikipedia page does not currently list them as part of the Seasons. And BritBox lists them as separate titles completely, having to search and see them separately from the seasons entirely.