Zombie Horses (and Zombies riding them) now spawn in the End Dimension at y=0

After updating my world from 1.21.11 to 26.1, I noticed that Zombie Horses + Zombies riding them are now spawning in the End.

This only seems to happen if the player is a certain distance away. No datapacks are enabled, no mods are installed.

Steps to reproduce:

• Download the world from attachments (I deleted the Overworld and Nether dimensions to save space)

• If you aren’t spawned on the end of a leaf platform, run

  /execute in minecraft:the_end run tp @s -4.54 1.00 -279.41 -89.98 6.51

• Wait.

• If Endermen spawn, run

  /kill @e[type=!minecraft:player]

  The timing seems to be completely random. Sometimes they’ll spawn, sometimes they won’t.

Expected result:

• For Zombie Horses to not spawn in the End

Actual result:

• A Zombie Horse spawned.