Same here on Win11. And if the windows is active, the left tab overwrites the rounding. The text color on inactive tabs are white and unreadable.
Inactive windows looks better.
Single tab with no painted tab, also unreadable.
1 Simply offset the left tab a few pixels to then right to fix the rounding.
2 Why is the no accent color on active window, active tab?
3 How do I get correct text color?