Mobs don’t spawn in portals

Currently slime farms can be easy if you make a perimeter: just place portals across the chunk and afk high up. You can make it more efficient if you use update suppression. If mobs don’t spawn in nether portals then we won’t have OP mob farms that can ruin the vanilla aspect of the game. This will also mean less people exploit update suppression (which is clearly a game changing bug that should not be vanilla). 

The way it should be done is that there should be a gamerule called ‘doPortalSpawning’ which if true means that mobs spawn in portals. The default should be false. This means that if someone has spent years building portal farms in survival, they don’t have to create/download mods that undo these changes, and have to update the mods just to get new features from new updates.