Here what we learned while we were designing the new MagSafe wallets.
While the new iPhone 12 series are compatible with Magsafe wallet, Apple states that the back of the iPhone doesn't has to be covered with any metal or magnetic materials except MagSafe. Though weak magnets are not likely to kill the smartphone, there is a possibility they will mess some pretty important aspects up. For example magnets from other materials then in Apple guidelines create magnetic fields that may affect the rear -facing camera with optical image stabilization.
Choosing the MagSafe accessory make sure that the manufacturer follows those guidelines, and seller knows what the product is made from. Apple recommends manufacturers that are producing the magnets according to their strict guidelines, with one of wich we are cooperating.
Same it's important that in MagSafe wallet were used magnetic shield with accordance to the Apples recommendations to keep safe the credit cards, as magnetic field can erase information from your credit cards magnetic stripe. More information about it here.