Our Rat Terrier doesn't think he has completed his daily terrier work until he has been flipped several times by both our GSD and our mid-sized classic mutt. The Shepherd has figured out ways to handicap himself in order to keep the wrestling match even with someone about 1/5 his size. It is most entertaining to watch.
I know what you mean. My ex had two Maltese (Malteses?) that were full grown when I got my Shepherd at 7 weeks. As a puppy, he started playing with the Maltese as "equals" and as he rapidly grew, he seemed to adjust his energy level accordingly when dealing with them.