I've seen this bug for many versions now, and I finally decided that I should at least report it and hope it gets patched.

Entities traveling at higher speeds can sometimes phase through blocks that are smaller than 1mx1m.  I have provided a clip showcasing this below.  In the clip, you can see that I am hitting an Endermite with a knockback 3 shovel.  It manages to phase through the fence.

https://i.imgur.com/E5Wsyy0.mp4