Two chargers rated at the same wattage can still charge a phone at very different speeds, and the wattage number rarely explains why.

Two USB-C cables can look completely identical and still perform nothing alike. The difference usually comes down to a chip smaller than a grain of rice.

Two USB-C chargers can look the same, cost the same, and still charge at wildly different speeds. The difference lives in the USB Power Delivery negotiation, not the plug.