When a world is on easy mode, nether portals will never spawn zombie pigmen. Normally on easy mode they should spawn very rarely, but it still happens. This breaks gold farms for a significant amount of players on bedrock.

How to reproduce.
1. Build a max size nether portal in the overworld
2. Light the portal and set difficulty to easy
3. Set your random tick speed to 1000 (or higher because why not)
-You should see no pigmen will ever spawn from your newly built nether portal
4. Set difficulty to normal/hard to witness an ocean of pig people summon from the portal.
5. Set to peaceful before they overtake your entire world