Hoglins/zoglins with the glowing effect sometimes show black dots

Are you sure this doesn't affect other mobs? This might be MC-96154. Not every mob is affected, but many are. There is a list of some affected mobs in MC-169921, which I created a few months ago. I was told that MC-169921 was a duplicate of MC-96154 and that it's caused by outdated graphics drivers. A possible explanation for why the hoglin isn't affected in 20w13b but is affected in 20w14a, is that the model and/or texture might have changed (slightly). Similarly, villagers aren't affected in 1.13.2, but are affected in 1.14 (and later), which I assume is because the villager model and/or texture changed.

I tested this with all mobs (except for hoglins/zoglins), and the glowing for them renders fine. The glowing outline renders fine for mobs such as strays, villagers or even drowned. Not sure if anyone is also having the same issue as well.

Does this occur in 20w45a or is it blocked by MC-204782?

Happens in 20w46a too.

Can confirm in 20w49a using: Nvidia GeForce GTX 1660, Intel Core i7-2600 @ 3.40GHz
Feel free to use these commands to reproduce, as it makes life slightly easier:

/summon minecraft:hoglin ~ ~ ~ {Glowing:1b} 
/summon minecraft:zoglin ~ ~ ~ {Glowing:1b}

Updated 👍

I can confirm using Apple M1. Here's a video of this issue occurring: https://youtu.be/ish7Z-EIDqM

I confirm in 20w51a

that black dot appears on end of hoglin's and zoglin's hair and other one zoglin's broken leg has appear instead

Can confirm in 21w03a using: Nvidia GeForce GTX 1660, Intel Core i7-2600 @ 3.40GHz

Can confirm in 21w07a.

Can confirm in 21w15a.

Can confirm in 21w17a.

Affects 1.17 Pre-release 2

Affects 1.17

Can confirm in 1.17.1.

Can confirm in 1.18.1.

Can confirm in 1.18.2 and 22w11a.

Can confirm in 1.19.

Can confirm in 1.19.2.

i can confirm in 23w51b

Confirmed in 1.20.5 Pre-release 1