Nick Statt, The Verge:

Apple’s new iPhone 12 line will be able to access faster wireless charging speeds of 15W in line with the most up-to-date Qi standard, but there’s a catch: you’ll have to use Apple’s new MagSafe brand of charger or a MagSafe-compatible one from a third-party accessory maker.

Interesting. Hop over to the iPhone 12 technical specs page, then down to the Power and Battery section (about halfway down the page):

• MagSafe wireless charging up to 15W
• Qi wireless charging up to 7.5W

Yup, only MagSafe gets the full 15W. So if someone did come up with a magnet case for older phones, they’d likely solve the click-in-place problem, but not sure they could offer access to the faster charging.