How to make a new Nether Portal without letting it link to a another Nether Portal?

I have read up on this issue as much as I possibly could. I even tried it on the PS4 version of Minecraft and have had no issues with it. I am now trying it on the iOS Minecraft version (which is Bedrock I believe).

So this is the issue:

My current portal (overworld portal) is at these coordinates. X:830, Y: 63,Z:645. I know the rule is roughly that your X and Z coordinates must be +/- 128 to make it so your portals don't link and you finally get a new portal location. I want a new portal so I can have a better chance at finding a nether fortress.

Therefore I made my new portal at X: 447, Y: 68, Z: 900. This obviously is more than the 128 blocks rule, but it still didn't work. I went through the portal, which sent me to the same nether portal that was created from the original overworld portal I made. Am I misunderstanding something? I did the same thing on the PS4 version and it worked normally.

The 128 blocks distance shows where where the game searches for existing portal to link to. The number is the same in the overworld and in the nether, but there is an important consideration when calulating the result. One block in the nether corresponds to 8 blocks in the overworld. So by moving 128 blocks in the overworld you moved only 16 blocks in the nether. This is still less than 128 so the game finds the existing nether portal and sends you there. To move more than 128 blocks in the nether and force a new nether portal, you need to move at least 1024 blocks in the overworld. Frankly, depending on your gear it could be easier to just walk in the nether.