I think what makes One (level of abstraction) the magic number here is that Zero is too few and Two is too many.
Swapping a logger behind a logger facade (number of levels: 1) can possibly result in some user benefit, such as the new logger can do something that the old logger can't. I can imagine that it could be performance, supporting certain types of appenders, etc.
It's much harder to imagine the user benefit from swapping a logger facade (number of levels: 2).
(And if the number of levels is 0, then it's probably just bad object-oriented design: you'll have thousands of places in your code where the logger is referenced and what if there's a breaking change in the next version of the logger.)
The deal with logger facades appears to be that you have to pick one of the third-party options or to create your own and prepare to stick with it for a long time.
