Description
The issue occurs regardless of the theme, but it is highly visible when using a dark theme. I used All Black - Full Dark Theme/Black Theme in the attached videos to make the borders more obvious.
In the Release version, turning on this option makes the border disappear completely.
In the Nightly 1.94.42 or later, turning on this option leaves the border artifact behind.
Steps to Reproduce
1 Optional Install and apply All Black - Full Dark Theme/Black Theme to make the borders clearly visible.
2 Go to brave://settings/appearance
3 Turn on Show rounded corners on main content areas
Actual Result
Release version The border disappears.
Nightly version The border remains.
Expected Result
In the Nightly version, the border should disappear completely when the option is turned on, just like it does in the Release version.
Windows11 Nightly 1.94.42 or later