in linear systems, they are the same thing. To get the minimum reflection coefficient, you cancel out the reactive part of the load impedance, then match the remaining resistive part to the 50 ohms test impedance.
It only gets cloudy in things like a power amplifier, where you really do not have an output impedance to even test until it is loaded properly (large signal S parameters). And in a power amp, the match at the harmonics makes a difference too.
Another cloudy case is a lownoise amplifier front end, where you deliberately mismatch the input impedance to operate at the region of minimum noise figure.