Did iOS 12.1.3 break iPhone 8 working with iPhone 7 Smart Battery Case?

Has anybody else experienced this?

I've been using the iPhone 7 Smart Battery Case with my iPhone 8 for months with no issues. The battery case would discharge first while using it (saving the iPhone battery), and it charged right up using any charger with no problems.

I upgraded the phone to iOS 12.1.3 recently, and now I noticed the battery case doesn't seem to work properly. It doesn't charge with the phone in it (but charges correctly by itself), and when I use it, I notice the iPhone now discharges first.

This website by Apple seems to imply you can't use a Smart Battery case with the iPhone 8 and iPhone X.

Can anybody confirm whether they have the same problems or is their battery case working properly on an iPhone 8?