>>479804They tried to get in as many grain products as possible and gruel or pottage is one way of doing that. However bread also was an important food, all villages had either a peasant with a large commercial oven or a communal oven of the feudal lord. Remember those prayers that say "Give us our daily bread" that's quite literal.
As for storage, gruel contains moisture and will spoil even quicker than bread if you don't keep it constantly heated.
>pic related, that bulbous clay work thing on the right hand side of the farm is a commercial oven. 