Iphone 11 Camera Megapixel downgraded

Hello !

I just updated to ios 15 and upon exploring the updates on my iphone 11 on photos, they added an “Info” button that shows the information like resolution, date, time, camera lens used and file size. However, I was surprised that the mega pixel shows only 9 instead of 12 as advertised. When I checked back the photos taken to the date when it was newly bought, it show 12 megapixel but 5 months after, the photos are all in 9 mega pixel up to today.

Why and how come it downgraded from 12mp to 9mp? Is it because of the ios 15 update? and to be honest, it’s not fair. I feel like I’m scammed. Not only me but the other iphone 11 users as well. Can somebody explain this?