Funny thing is Rick my typhoon sitting on my dinning room table acquirers satellites faster then outside. I have no problem running GPS indoors if I wanted to. The rule of thumb is turn off GPS as you never know when you might lose it. Learning to fly with out GPS is the best.
I would say no although this is just a guess but I would say you would get that big red warning on your ST10+ saying you have lost GPS connection just like when it happens outdoors which would mean you are now flying without GPS control. Very annoying having it buzzing and flashing when your trying to fly without GPS. Had that happen going under a metal bridge once.
The motors only require the GPS lock to start (when it's not disabled). However, that's only to originally start the motors. Once they're started, you're fine.
If you're flying and you lose GPS lock, the quad doesn't just crash out. It instantly beeps at you, flashes on the controller, and goes to full manual mode. That means that you have no stability from the GPS, so you are now at the completely whim of the elements. It's not the same as angle mode, because now you have to control every aspect and adjust for everything, every breeze, and so forth. So while indoors in say, an auditorium, you won't have wind blowing you around, you DO have to fight that outside if you lose GPS lock.
Also, outside, it WILL still keep trying to get a lock, but until it re-establishes, you're manual.