grammar - How these clauses are co-ordinate?

In Wren and Martin, there are examples given in which "who" introduces a co-ordinate clause which thus can't be an adjective clause.How's this possible.

E.g

1)I met Mr. Joshi, who thereupon shook hands with me.

In this sentence isn't the clause "who thereupon.....me" telling us more about Mr. Joshi ?

2)He relaeased the bird, which at once flew away.

The same case here ? How it's a co-ordinate clause and not adjective clause ?

But look at this "This is the boy who broke the window". It's written in the book that here "who broke the window" is an adjective clause.Isn't same as the above two examples ?