Why is a Fibonacci-Tree of rank 1 consolidated with one of rank n in this Fibonacci-Heap?
Page 8 defines rank: 


  rank(x) = number of children of node x


So rank is not the height of the tree. With that, each chain, regardless of its length, has rank 1 and will be consolidated with any other chain.

But in most cases, rank defines the height, so why is it different here? The Reason is, it is simpler to implement. For the number of children, you just need the size of the direct children of a node, in many cases just some array.size, often already saved in a field.

But for the height you'd need additional calculations and fields, which can get complicated, especially for functions like decrease-key (which would make it not O(1) anymore).