Pretty sure you are wrong.
Don't see how a dog is "under stress" when it's happy.
Did you even read how my bitch's tail fuzzes up when I get her food?
What "stress" is she under, running around in circles, happy as fuck, uber-excited about eating?
What about when I grab a toy and she does the same thing? She is EXCITED, nothing more.
Regarding the fuzzing issue, I can't possibly fathom how 1) anyone can conceive of this is always a "bad sign" ... nor 2) how in the world it "means nothing."
It may not mean GAMENESS ... but it sure as shit means SOMETHING.
They don't do this relaxed. They do it when they're amped-up, challenged, or excited.
It may simply be a reaction to a shot of adrenaline from the adrenal gland (fight or flight).
In a game dog it means "fight" ... in a cur dog it may mean "no more" ... but it damned sure means SOMETHING ... and that "something" may indeed vary, so there may well be no "one" answer.
To universally say it's a bad sign is simply wrong IMO ... and perhaps so too is it wrong to believe it's always a good sign.
It may simply be the body's response to a shot of adrenaline, over which the dog has no control, and how that dog handles the adrenaline shot may well be up in the air ... and individually dependent.
Jack