Not necessarily misleading, the switch both operates the brake lights and can be used to tell the ABS module or PCM that the driver is indeed stepping on the brake; stability control and hill start assist both need to know that. It probably does a circuit check when you start the car, found a fault, and disabled those systems (and put the warning lights on) because it can no longer be sure of the state of the brakes.
It’s also of course is what tells the computer that your foot is on the brake so it unlocks the shift-lock solenoid. If the switch had failed in such a way that the self-test didn’t detect it (i.e. if the switch came loose and the little plunger wasn’t hitting the brake pedal arm anymore) then you would have had the shifter locked without any warning lights.
Thanks! 
And per your post above, I did not mention to the dealer about having taken taking it anywhere else.
Sorry, I meant misleading in the sense of the overall problem wasn’t specific to ABS/Hill Assist.
eh, that’s the nature of on-board diagnostics. They can only say “hey, there’s a problem over there.” it still takes a trained meatsack to figure out what’s causing the problem.
incidentally, this is why a lot of auto parts stores will offer free trouble code checks. They hope you’ll buy a ton of parts from them trying to find the problem with your car.
After coming on for maybe a day at a time a couple of times, and then resolving themselves, the lights were back on for a week. I took it back in and they confirmed that the new replacement part they had put in had failed. But, Subaru had acknowledged it was defective so now they had a new improved part to put in. We’ll see how long it lasts!