As a user I don’t think “Where to?” make it faster for me to arrive my destination, for me it was easier to ask for the ride and as the driver was getting closer to my location then I put my destination. Just think the process it took in the past: ask for the ride, and while the driver was coming you enter where you are going, for me it saved time that way because sometimes I just got in the car and told the driver the directions to my destination but I was already inside the car so no wasted time in checking is the final address was correct. Now you have to put the destination, check it’s the correct place and after that you ask for the driver, how does that make the experience better and faster?
Also, I’ve asked for an Uber Pool and get in with people that were using the app for the first time and didn’t even know what Uber Pool was about, they just saw it was cheaper and went for that option. I think you are assuming people knows stuff that they don’t and making more complex the whole experience.