MrHappy,
I think what is happening w/ the drone comb building you refer to is that in an established colony of bees when a hole occurs for some reason or other, such as mouse damage, for some reason unknown to me bees will more often than not fill that space w/ drone comb.
Interestingly you will find that if you make a nuc w/ a queencell or set one up to raise its own queen, almost always any hole will be filled w/ worker cell sized comb. I have a friend who used to spend part of his winter going thru combs which he intended to use for spring nucs cutting out drone comb, sometimes just knocking out all the comb in a frame leaving the wires.