Not a duplicate of MC-74103, this is slightly different, and more recent.
When summoning a mob with an extreme follow range, all mobs in the world will freeze and become invulnerable, block breaking will not produce drops, and chat will not create output or take input. FPS is not impacted, however.
Linked issues
Comments 3
The comments on MC-74103 are addressing that yes, it can cause lag and that is normal, but they have not addressed that there is no way to undo this action as it freezes all mobs - I believe it can still be called a bug because after the mob is spawned the world will be permanently altered.
Same issue, same ticket.
Feel free to leave a comment in MC-74103.
Where's the difference to MC-74103 ?