The piglin and hoglin mobs' models had a bug where some of the surfaces did not appear and the surfaces that did appear seemed out of place. For example the back of the piglin was completely invisible except for the legs and the face of the piglin did not seem correct. This was consistent in all dimensions and for all piglins and hoglins including the baby variants however this visual bug did not occur at all for the zombie piglins and zoglins, I could not get it to occur at all for any other mob. It also happened across 3 different worlds that I tested this with. The mobs still had the normal AI and the piglins could hold weapons and the like and the items held were where they were meant to be despite the piglins appearing to have no arms.

I have attached 8 pictures, one for each side of the hoglin and piglin taken in the Overworld (rest assured that this occurred in the End and the Nether). 

EDIT: After reloading the game, things remain exactly the same. As well as this, after updating Java to build 1.8.0_251-b08 (check Environment for the original environment) the bug still remained the same, check the recently attached picture including F3 screen.

EDIT 2: Bug persists even after restarting the computer. I thought it would be sensical to provide the JVM arguments that were in the launcher however I have not changed these at all. JVM arguments: -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M