It's really hard to describe how falling blocks looks, but it's extremely glitchy and definitely not right. See video for an impression: https://drive.google.com/file/d/18v3bEEL_1vL8wfFTvBg1IWmvG2Lh5YAA (Downloading does work, even if it shows a weird error message.)

Also note that the hitbox has two diagonal lines for some reason.

Also affects falling blocks with regular gravity, that's just harder to show.

This does not happen in 1.14.4.