And, to to get more meta, why didn't the OP ask the Disney staff what the fingerprint was for? It's not that hard of a question and you have to be 99.99% certain that the staff is trained to handle questions like this.
I'm sure he thought about this question the entire visit before rushing home to write an urgent blog post, which is sad because it probably ruined his trip a little.
My experience generally with front-line staff making people follow policies is that they have no idea why the policy exists. I expect to have to go up one or two levels in the hierarchy before I find somebody who can talk sensibly. So I could understand him not bothering.
Also, he was clearly startled the first time, and then mad the second time. The blog post may have only occurred to him later.
FYI, I visited on a multi-day pass (4 days this last week). I didn't rush home to post, in fact, I did it on my last night after packing for home so I wouldn't lose the motivation and things were still fresh in my mind.
Also, the front line staff was pretty clueless (IMO). I was told it's for our 'guest's convenience'. However, I didn't really engage in a deep discussion with them because my family was waiting to have the fun I promised.
I'm sure he thought about this question the entire visit before rushing home to write an urgent blog post, which is sad because it probably ruined his trip a little.