Keybind conflict warning is not shown when rebinding existing controls to B

The bug

When two controls are bound to the same key, Minecraft generally colors the text red to indicate a conflict. This, however, does not happen when assigning controls to the B key, despite B being the designated (and hardcoded) key used along with Ctrl to change narrator settings.

How to reproduce

1. Hold a stack of items
2. Change your drop key to B, paying attention to the text color on that button
3. Ensure "Narrator Hotkey" is on in Accessibility Settings
4. Use Ctrl+B when holding the stack of items

Expected results

Ctrl+B causes the narrator to be toggled and the whole stack to be dropped at the same time. As a result, some sort of warning about a keybind conflict would have been raised earlier.

Actual results

There is no such warning.

How to fix

Fixing MC-264903 would also fix this issue.