What I like about the Black philosophy is that it wants to make code style _uninteresting_. People should think about other things, not formatting. That's a great goal. So it seems to me that the best style choice is the most _boring_ choice. The least creative, least novel way. It should try to avoid inventing new formatting algorithms.
What's the most boring way to format a string literal?
The way the language already does it. The way every Python programmer has already seen string literals formatted from the very first day they started typing things into a Python interpreter.
Even if half of us liked single-quotes and half of us liked double-quotes, you can guarantee that every Python programmer on the planet has seen and lived with strings that are formatted the repr() way, including the double-quote fans. You can't guarantee the opposite.
No one could fault you for doing it the repr() way. Blame Guido :) he made that choice decades ago, and everyone has already had to make their peace with it. It's a solved problem. For anyone writing a program that emits Python code, it's the default way to format a string. It's the least assailable option, and that's a good thing.
How does that sit with you?