
Think it can happen for a number of reasons and you need to watch what
else is going on as well....
Fr'instance...
Rocky will run up to a strange dog, sniff, and then he will paw on shoulder/back and go quite stiff, slow tailwag...
This is from him a testing thing, he wants to know if that dog will submit straight away, if it does so and does it in an over the top 'woe is me dont kill me i am a pathetic little flower'...... he'll kick its ass.
If it shrugs the gesture off but is polite he will be nice.
If it tries to do it back or objects strongly again he will kick its ass.
(as a result he isnt allowed to meet strange dogs!).
Other dogs will do this as a slightly over the top method of seeing who is fun, who is mean, who is boring etc, with no serious interest in 'status' at all.
That said, i have yet to see a very submissive meek sort of a dog do it to a strange dog.
Em