This is best seen when outside of the world border and at a corner. When in the demonstrated position, a section of the world border that extends into solid block territory and is usually not visible as a result ends up being visible.
MC-226844
Underground/occluded sections of the world border are sometimes visible
Open
6
(Unassigned)
Confirmed
Rendering
1.16.5, 1.17 Pre-release 1, 1.17 Release Candidate 1, 1.17.1, 1.18 Pre-release 1, ..., 23w14a, 23w17a, 1.20, 1.20.4, 24w04a
Retrieved
Can confirm that this is an issue. Also affects 1.16.5 along with 1.17 Release Candidate 1.