Seems there might be a bug on the way how edge displays the highlight color of an expanded tab group.
First the color seems to appear at the top (unlike chrome) of the tab which is very encounter-intuitive, but this is just my opinion, but the problem I have is that the line color is either out of place or overlaps. I think this may be caused because edge seems to use some shadow on tabs which somehow messes up the line.
Check below the image.
The edge version is: - Version 106.0.1370.47 (Official build) (64-bit)