15w wireless charging for iPhones is new. Previously wireless charging maxed at 7.5w
Yes, to me, the big change here was that it allowed for much higher wattage wireless charging, which should be closer to a wired "fast-charge" in terms of speed.
Android phones have had 10W+ wireless fast-charging capability for awhile now, but Apple has been limited to 7.5W up until introduction of MagSafe.
My understanding is that ensuring the "perfect placement" with the magnets allows them to more safely charge at higher wattage without significant energy loss / efficiency loss from being off-center.