Some mob farms (e.g. gnembon's copper farms) exploit the zombie/drowned reinforcement mechanics to summon large numbers of zombies, which results in massive amounts of XP (and a lot of copper). All of them are likely to work at least once with this mod installed, though the spawner-based one would become unusable for a while once the zombies despawn.

From the Minecraft Wiki:
When a zombie spawns a new zombie as reinforcements, "both the damaged zombie and the new zombie has a 5 percentage point penalty to their 'likeliness to call reinforcement' stat".

To mitigate this being abused, as the rate of zombie reinforcement spawning increases,

• It becomes more likely for new zombie reinforcements to fail spawning (even if all other spawning conditions pass).
• The 5 percentage point penalty per successful spawn may increase, thereby decreasing the number of reinforcements that a single zombie can summon.