Cleric Spell Progression

I started playing with the Red Box Cook/Marsh Basic set. But by the time someone got their hands on the Expert book, it was the Mentzer version. Fast forward a few decades and I finally get a copy of the Marsh/Cook eXpert set, and was surprised to see the Cleric spell progression, it seemed like a typo to gain both level 3 and 4 spells for the first time at the same level.

I noticed that ACKs uses this BX progression for Clerics, and I am just curious on the story and reasons behind this progression is. If anyone knows why it was setup that way in BX, why it was changed in all other editions, and what sort of effects it has on the game.

a story told here: