I cannot remember ever attending a siyum of an order of the Mishna where the person making the siyum did not learn the last mishna of the last masechta of the seder. Is there some problem with learning the masechtot out of order or the mishnayot of a masechta out of order?
Assuming there is no problem, is it the common practice to learn the last Mishna of the seder at the siyum even if the masechtot were learned out of order? Or is my experience not representative?