New backup file way smaller than previous one?

[predation]

So last night I iCloud backed up my phone to do a restore.

Before the erase all, I did an iCloud backup.
The backup file size was around 37gb.

After I completed the iCloud backup, I continued to erase the phone and then restore from backup.

After the phone restored, It automatically backup into iCloud.

Now, my backup file size is like 8-9gb when I check on iCloud?? 8/50gb whereas previously it was 37/50gb.

I looked at the data that was being backed up and the photos shows like 30gb and it all being there. Am I missing something from iOS 11?

 

[predation]

So I talked to a rep and he said that iCloud Photo Library should be enabled.
I don’t have it enabled on my phone right now and didn’t have it enabled on my previous phones.

I don’t see a reason why this would have to be enabled to get the iCloud storage usage to what it should be at. I don’t want my photos being shared across my devices.

Is this an iOS11 mandated thing?