Black auto-explodes imports, collections, function calls, etc. when they contain a trailing comma:
https://black.readthedocs.io/en/stable/the_black_code_style/current_style.html#the-magic-trailing-comma

This means that even though this would fit into one line:

from seven_dwwarfs import (
    Grumpy,
    Happy,
    Sleepy,
    Bashful,
    Sneezy,
    Dopey,
    Doc,
)

Black will NOT convert it into this:

from seven_dwwarfs import Grumpy, Happy, Sleepy, Bashful, Sneezy, Dopey, Doc

As long as the import list contains a trailing comma.

Ruff currently does not have the magic trailing comma handling as far as I can tell and will collapse the import list if it can fit within the line length limit.

See relevant fixed (but not released) issue in isort: PyCQA/isort#1683