iOS 17.1 Bug - iCloud Using Cellular Data Despite Being Set to Wifi Only

I recently upgraded to iOS 17.1 on iPhone 13 Mini. My phone is now using significant amounts of data to do some sort of iCloud process overnight even though I have the settings toggled to only do backups and iCloud processes over wifi.

The amount of data it's using is insane. For example, last night, October 31, my phone used over 6.5gb of data between 12am and 6am!

What's more, the process isn't even doing a phone backup. The last phone backup I have is from October 29. The data usage statistics appears under Settings -> Cellular -> System Services -> iCloud. It's showing over 7gb used in a 24 hour period for iCloud.

What's more, I have iCloud turned off over cellular in two places. Once within Settings -> Apple ID - > iCloud -> iCloud Backup where I have backup over cellular selected as off. Then also under Settings -> Cellular where Wifi Assist, iCloud Drive, and iCloud backup are all toggled to off.

Apple support has been useless. The only recommendation was to toggle on and off and restart the phone. This didn't help.

This issue only started on iOS 17.1 and is now costing me a small fortune in data overages. This needs to be fixed immediately. My only temporary solution is to put the phone on airplane mode at night.