Description: An example of a mod that has this functionality is PlayerSkinsMob Mod, as it has an option to change the weight of their mobs being chosen for a spawner and another to completely disable/enable their mobs from even being considered in the pool. I know 1.12 isn't of the highest priority considering 1.16 has been out for 11 months. Sorry if my knowledge on how you guys inject or weight your mobs into the spawner pool isn't top notch as for all I know it could be another mod causing it for all i know.

Reference Image: https://imgur.com/a/YfBb9RT

Version I'm Running:

• Minecraft: 1.12.2
• Forge: 14.23.5.2855
• AbyssalCraft: 1.12.2-1.10.3

I just had a wonderful stranger give me a script that fixes this issue via Crafttweaker using nbt transformations, so I'll close this on the night of 5/21 (Central US) if no further comments are made. Feel free to close this earlier if need be as my personal issue is 99% solved.