No instead they will call you before the trip and ask you where you are going and then cancel the trip after hanging up.
If it is raining or the sun is out or the trains are busy or it is any of one a hundred random reasons - you will have surge pricing. Not just 10-15% extra but 100-150% extra. But don't worry keep standing around for a 30-40 minutes and checking the app eventually the price will come down...