Whenever a mob's AI tells it to jump, it will heavily favor the x-axis. This can easily be seen with spiders and cave spiders, as they will jump whenever they get close to you. You can also view it in wolves, but it is a little more complicated to set up. Other mobs may be affected, but I cannot find reliable ways to test them.

Steps to Reproduce in Spiders

1. Create a Redstone Ready Superflat world.
2. Spawn a spider/cave spider and aggro it
3. Run along the z-axis – the spider will jump at you
4. Run along the x-axis – the spider will frequently jump in place
5. Run diagonally along both axis – the spider's jump will heavily skew towards the x-axis.

Steps to Reproduce in Wolves

1. Create a Redstone Ready Superflat world.
2. Spawn a skeleton and splash it with a slowness potion
3. Spawn a wolf to chase the skeleton
4. Note that the wolf jumps similarly to the spiders above

Mobs also tend to rotate their bodies a lot when jumping, this may be related to this bug.