Middle sections of the pieces, such as Development, might be an exception to that because obviously composers wanted to avoid too much predictability. This is evident in much of the music by Vierne, Dupre, Franck and others.
But what if a composer wanted to create something really unpredictable, something which the listener and the performer would find interesting, flexible, and alive? What would happen if instead of 4 or 8 measure units, you could have 3, 5, 6, 7 or even 9? Moreover, one sentence in a period might have 5 measures and another - 4 etc.
Today's sight-reading piece is Andantino (p. 1-2) by Louis Marie François Andlauer (1876-1915), little known French organist and composer who worked at Notre-Dames-des-Champs and Eglise Saint-Eloi in Paris. This composition is taken from Two Short Pieces for Organ or Harmonium (1912). If you look closely to the score, you will notice asymmetrical phrases right away.
You can play this piece with or without the pedals. As you sight-read it, pay attention to the stops or cadences at the end of asymmetrical units. Here's how the piece is divided in measures: 6-6-7-5-2-2-2-5-7-6-6-2.
In order to achieve a fluent legato touch, you will need to use finger substitution and glissando techniques. The composer suggests soft registration so choose perhaps 8' flutes with or without 4' reinforcement.