MagSafe Duo charger imprints

This is how my iPhone 12 Mini Silicon (with MagSafe) case and MagSafe Duo Charger looks just after few days of charging. Imprinted ring not only on the case, but black imprints also on charger pad itself. You can even see burnt-in Apple logo from the case. So sad! And, no, you can't clean it off.

Is this... normal? I know that rings on Silicon cases have been reported as expected, but what about the MagSafe Charger Duo burnt-in stains. I have used this charger with 18W wall plug (also, as all other accessories, original from Apple).