I don't have Jyn unlocked yet, my Poe is weak, and I've never seen JKA stack exposes on himself, so I couldn't really say since I've never seen the phenomenon. I also didn't realize there was something wrong with Eeth Koth, because...Eeth Koth.
What's the difference between one expose and multiple? 1 expose = your shoulder sticking out from behind cover, while 2 = standing out in the open, and 3 = painting a bullseye on your chest? (Pretty sure that's exactly it actually)