Another martial artist who has mistaken fighting for self defence. "Bad guys" don't "fight" you. They use the four d's (Dialgue, deception, distraction, destruction) to take you out of the game before you even knew you were in it. They don't want to fight you, they want to take what you have with the minimum amount of fuss and risk.
The only time you are likely to find yourself in a fighting stance is if you agree to step out side for a square go. But that's street fighting, which is illegal, and has nothing to do with self defence.
As for all the talk of leaving yourself open to heel hooks, trained martial artists are not in the habit of agreeing to get into street fights with other trained artists, for one it is likely to be in the T&C's of your club that you will be thrown out for brining your association, art and club into disrepute.
Could you be attacked by a trained martial artist, yes. Is it going to be the sort of illegal activity which poses the biggest threat to your personal safety, probably not. Certainly not to the point that you need to devote large amounts of training into learning how to defeat people from other arts.
Fighting stances are for fights, either in the ring, the cage or the pub car park. Self defence however is a totally different ball game, and believing your physical prowess in the ring, cage or dojo is going to transfer into SD success is like believing table tennis lessons will help you win Wimbledon.
Just ask Maiquel Falcao And Kaue Mena.