The developers have decided to finally update the models.
Mojang has introduced the "26.1 Snapshot 2" snapshot for Minecraft. They have decided to add updated models of mob cubs to the game.
Game Director Agnes Larsson explained the developers' vision:
Until now, mob cubs were just smaller versions of adult mobs, but with bigger heads, but now our artists have created unique textures and models for them that give each cub its own cute look and personality.
In total, Minecraft introduced eight new versions of mob cubs.
Usually, mob models have eyes consisting of two pixels, but now the cubs have only one pixel, which adds to their "cuteness".