Grouping of tabs appears to be broken in all builds including latest beta (1.23.58). This is best seen while in “light” mode rather than “dark” mode.
See reddit post from a different user here for screenshots: https://old.reddit.com/r/brave_browser/comments/mh82ow/i_love_brave_but_we_should_update_the_tab_groups/
In particular, please notice the intersection of the vertical lines of the in-focus tab with the horizontal line of the adjacent tab(s) and/or group title.
This bug is also present on the latest public build (1.22.70).