Small correction: 45W charging for Samsung phones requires 9V/5A, not 15V/3A. This is also the reason many reviewers don't measure this speed. If either the cable or charger doesn't support 9V/5A (with most supporting higher voltages, but only at 3A, like the cable included with the phone...), the charge speed is limited to 25W max. This corresponds with the 23W measured here.
Using a 100W and 5A rated cable with a PPS charger doing 65W and 5A, I get 45W for the first part of the charge curve, after which the phone slowly limits charging to a lower wattage.