So, let me see if I get this correctly
Step One : public announcement : drivers will get 100% of their tips.
First off, if you have to announce that, there's already something wrong.
Then, second step : switch to variable base pay rate without telling anyone.
Ok, for that to happen, there had to have been a meeting. Someone chaired a meeting with a group of other people and the question was, specifically : how do we not pay 100% of the tips, like we promised ?
And all the good little soldiers brainstormed that little switcheroo.
The next question was : how do we keep the drivers from learning about it ?
Well, at that point, anybody could think of lumping all the tips together without any possibility of checking which tip for which job. The less you communicate, the easier it is to hide things.
What this whole story tells me is that Bezos is far from being the only evil one in Amazon. He's got an army of evil minions who have absolutely no morals at all, and they're all in upper management.