Mariah captured what I am seeing as well (thank you, Mariah!). I'm able to mitigate it by turning VSync off, but this wasn't necessary in prior versions.
Also on Mac Java Edition, seeing the same when moving (glitching horizontal line in bottom third of screen); it started after upgrading to 1.14.3. Turning VSync off reduces/eliminates it.
Also reported in MC155120. Turning VSync off helped some folks, but not everyone.