I do something similar for multiple-choice questions : I point my finger to 2 or more locations (in front of me, on my computer screen, …), with each location associated to one answer, and I let them guide my finger toward the location of their answer. If they guide it nowhere then no answer is right.
For exemple, I’ll ask them if they prefer “something” or “something else” or “something else entirely”. I’ll point to my right and tell them it’s for “something”. I’ll point in front of me and tell them it’s for “something else”. I’ll point to my left and tell them it’s for “something else entirely”. And I let them choose without interference, like you do.
It’s faster than just yes/no questions. With practice, it gets easier and I often know what they’ll choose before they indicate it.
It’s also something that works great for me when I use subtler methods of communication and I’m not sure my mind is blank enough and that I’m not polluting what I feel. Having to focus on letting them manipulate my finger shut my mind effectively.