$ ruff version
ruff 0.12.7

$ ruff check --isolated --config 'lint.pyflakes.allowed-unused-imports = ["os"]' <(echo 'import os')
/dev/fd/63:1:8: F401 [*] `os` imported but unused
  |
1 | import os
  |        ^^ F401
  |
  = help: Remove unused import: `os`

Found 1 error.
[*] 1 fixable with the `--fix` option.

$ ruff check --isolated --config 'lint.pyflakes.allowed-unused-imports = ["os"]' <(echo 'import os.path')
/dev/fd/63:1:8: F401 [*] `os.path` imported but unused
  |
1 | import os.path
  |        ^^^^^^^ F401
  |
  = help: Remove unused import: `os.path`

Found 1 error.
[*] 1 fixable with the `--fix` option.

$ ruff check --isolated --config 'lint.pyflakes.allowed-unused-imports = ["os.path"]' <(echo 'import os.path')
All checks passed!