Massive mob freeze and magically working non existent portals

Ok so there are magical non existent nether portals

What I expected to happen was for the polar bears to stop spawning into the nether after I broke the portal

What actually happened was that the polar bears continued to spawn

Steps to Reproduce:
1. Make a nether portal
2. Hook up a repeater clock to a dispenser filled with polar bear spawn eggs and make sure the polar bears get spawned into the poral
3. Tada! The portal magically tps the polar bears after you break the portal in the nether

Ok so there are a couple hundred frozen polar bears

What I expected to happen was for the polar bears to move a lot

What actually happened was that the polar bears froze for a while but I could still hit them, indicating that only the polar bears were affected (pigmen were also affected). They kinda froze like how an entity would react after being given 1 for the NoAI tag

Steps to Reproduce:
1. Spawn a ton of polar bears like how I showed you above
2. Go in and out of the nether via portal
3. Hope Step 2 brings you to the same result

Btw if you're confused (cos idk how to write proper details) you can refer to this video which I posted (trust me I'm not looking for attention this is a real issue) https://www.youtube.com/watch?v=RklclU2JgfM