The Apple MagSafe Charger is a convenient way to charge the Apple iPhone 12 Pro wirelessly without worrying about proper wireless coil alignment but don't expect fast wireless charging compared to USB Power Delivery (see here for how the same phone charges using USB PD).
Using the GRL-C2 USB PD Tester and GRL-PSP Power Analyzer software from Granite River Labs, we can see that it takes about 5.4 hours to charge to 69% battery and the battery charge never goes beyond 69%. The MagSafe Charger charger briefly pulls 12.5W but uses about 5W for most of the main charging cycle. This means that the Apple iPhone 12 Pro is only getting about 3-3.5W power wirelessly for most of the time, which explains the slow charging. After 64% battery, power is reduced to zero regularly to more aggressively reduce the phone temperature but this also reduces the charging speed dramatically.