Black and White magic brush

What problem do you see this solving?

When working with black and white images i often see situations where the magic brush could be amazing but it only separates between colors and not grayscale tones.

If there is a subject against a colorful background, the magic brush is useless but in black and white, selecting by tone brightness can be very efficient

When was the last time you were affected by this lack of functionality, or specific tool?

Almost every black and white photo i edit