When you change your Dash key bind you aren't able to sprint by double tapping the forward key. Sprinting with the left control key still works.

Fixed for fabric 1.18, not yet for other versions

Assigning the dash keybind doesn't disable double-tap dashing, but if double-tap dashing is disabled in the config it should restore double tap sprinting. I've tested in-game and can confirm this doesn't work. I'm looking into this.