This just started when I joined 18w43b (I can still play earlier versions with visible mobs). I didn't even know 18w43a existed, and haven't played that yet. I could play with mobs visible on 1.12.2, 1.13, and 1.13.1 (no idea that 1.13.2 existed until 18w43b). It's not that. They also retextured alot, so that may explain it.
Zack Clingenpeel
This just started when I joined 18w43b (I can still play earlier versions with visible mobs). I didn't even know 18w43a existed, and haven't played that yet. I could play with mobs visible on 1.12.2, 1.13, and 1.13.1 (no idea that 1.13.2 existed until 18w43b). It's not that. They also retextured alot, so that may explain it.