Sure, but that's been handled in Disney queues - and queues all over the world - for as long as queues have existed, long even before DAS. I don't think people are confused about how to handle emergency bathroom situations. I had to duck out of the Test Track line when my oldest was 4 years ago for a bathroom situation, and it was handled just fine without any heads up to the cast. I think it's more for people who have other (and more specific) needs that may or may not need to be accommodated while waiting in line. Someone in this thread posted that they needed to leave because of back pain, so their entire family got out of line and the CM wouldn't give their entire family a return time. But that's the thing - the whole family isn't supposed to leave together - just the person who needs to get out of line, and perhaps one person to accompany them (depending on size of the party and the needs of the person). Why on earth would he think his entire family would need to leave because HE has back pain, you know? That's like taking your entire family of 8 out of line because your 3 year old needs to go potty. But since there was obviously confusion on his part, and knowing that his back pain was a possible hinderance to waiting in line, I don't understand why he wouldn't have asked for the specific procedure before getting into the line. "Hey, I have a bad back that sometimes acts up if I stand too long. If it starts flaring up during my wait, what do I need to do?"
Or even more specifically, I think it's best to talk to CMs when you already know that you (or a member of your party) cannot wait in the SB line at all. That way the CM can tell that person what to do while their family waits in SB and then how to meet up with them at the appropriate time as they get closer to the ride.