You most likely don't see a difference because the phone has already plenty of charge. There is a charging curve, the phone will charge at 45 watts (~9.000mA) from 0-20%, then bring the wattage down to 37 watts until around 45%. From 45% to 60% it will charge at 30-35 watts, and above than it will be close and below 25 watts. So above 60% there's no difference when charging with a 45w or a 25w charger. A current of 4.600mA that it has shown is around 23 watts of charging power. Unless you charge your phone in quick burst, you won't need a 45w charger if you already have the 25w one. Though it will get you faster times from 0%-40% (in about 17 minutes) as the 25w charger would need around 25 minutes. Finally, if you try and see the current input while the phone is charging below 20% and you see a number of 8.000+ mA, you will notice it drop every now and then for a few seconds. That's normal. That's how Samsung manages the heat when charging at 45w.
I've bought a 25W GaN charger, for my S22. The super fast charging doesnt seem to work, no indicators. And according to app it max outs at 15W. Hearing rumours that Samsung nerfed their devices through OneUi 6.1 updates, to only accept original chargers to benefit full potential of charging.
