Quite right you are and I wish you all the best for your recital! I am one who likes varied programmes and by varied I do not mean eccletic. I mean, for example, Bach-Haydn-Beethoven-Schubert-Shostakovich.
I would say what happens is that for one reason or another (pieces too short to be published separately, pieces that centre around one subject - like teaching - or simply posthumous collections that owe nothing to the composer) a whole collection is is gathered together, like the Inventions, the Sinfonias, the Well-Tempered Klavier or, for that matter, Chopin's Preludes (and by the way I DO like two or three of them
) or Songs and for some reason these works that were published together are suddenly expected to be played and listened to together, as if they suddenly had become one work. The Well-Tempered Klavier is not one single work (or two, because there are two volumes), but a collection of Preludes and Fugues. Any one of those pairs is a work of its own and has even been given its own BWV number. While I would not dream to play one of the preludes without its corresponding fugue, I would avoid at all costs playing two (or three or four...) pairs in any fixed order.
One frown upon people who listen only to the Clair de Lune or to the middle movement of Mozart's Piano concerto No 21, yet we accept people who, in the course of two evenings, play the whole Well-Tempered Klavier or Beethoven's 6 quartets op 18.
It brings to mind my father's comment, many years ago, when he saw such a programme (Chopin's complete Etudes it was). "Imagine losing count after the sixth Etude!")