If you find a naturally occurring village in the later snapshots, you'll find there are absolutely no farmer villagers. As well as this too many clerics and librarians will spawn (even if there are no churches/libraries). Blacksmiths/butchers will spawn normally, in other words, if there is a blacksmith shop/butcher house, there will be a blacksmith/butcher.
THIS ONLY AFFECTS DESERT VILLAGES, regular villages seem unaffected by this? <---(another possibility is that it only affects villages which have a blacksmith shop/do not have a butcher shop)