I've always chuckled at that description of Barton Cottage, as being defective, and attributed it to Austen's sense of humor. In the Annotated Sense and Sensibility by David Shapard he says this is "irony at the expense of the common Romantic celebration of irregular, rustic cottages which this period witnessed as vogue among the wealthy"

Shapard points to "a new form of cottage, the cottage ornee (from the french for adorned or decorated)" and Austen's has one of these dwellings in Persuasion and Sanditon."These cottages were larger than traditional cottages and contained more amenities..but they did incorporate rustic elements"

So yes, they had more "sense" to them. Does anyone know of a floorplan of Barton Cottage?