I am on an iPhone 15 Pro and using the manual mode with 3x zoom, however when setting the iso and shutter speed and take a photo, the info of this photo is not the same as how I set it when viewing it in the Photos app.

Hi there, thanks for your feedback.
This happens if you have Smart Processing set to either High or Balanced in Settings → Formats & Quality. This is a limitation of the iOS camera pipeline, the system will “improve” your choosen parameters if any processing is happening.
We will make the limitation cleaer in the future.
