Is the MagSafe Duo Charger compatible with the iPhone XS?

I was given the MagSafe Duo Charger for Christmas but my iPhone XS barely charges on it. Maybe just 10-15% overnight. According to the Apple store, the two devices are compatible. But the Apple support pages imply that the charger only works with the iPhone 12.

I have the correct power adapter and I‘ve tried charging with and without the case on my phone. I have a non-Apple wireless charger that works just fine with the phone in its case.

Thanks!