I largely agree with this logic per my other comment [1], but I think your analogy leaves out an important element (as does mine!), which is that the converted version only lives within Amazon's platform; it's not like Amazon is licensing you a tool that you can apply to anything and happen to use on an Amazon-published work.
So that makes it more like a derivative work Amazon is distributing than a client-side format shift.
So then, let me tweak your analogy a bit. Let's say a studio sells copies of a movie to theaters. They sell the color version and the B/W version, and different rooms/times might have one or the other. The theater sells out all the tickets for the B/W version, but can't any sell tickets for the color version.
Thinking quick, the theater management decides to sell tickets to a color showing as a B/W showing, and when patrons come in, they put some layer over the screen so it looks B/W.
In that case, I could kind of see how that would violate the copyright/license agreement of the studio -- you're selling showings of the B/W version you didn't purchase. [2]
Your scenario would be more like a customer coming in with filtering glasses that make it look like the B/W version to that customer only, in which case, yes, it would be harder to make the case that it was copyright infringement.
[1] https://news.ycombinator.com/item?id=20800777
[2] And yes, in practice, the studio wouldn't turn down the money, but let's say they're stubborn about it for some reason.