What affects the world is real. (If things can affect the world without being “real”, it’s hard to see what the word “real” means.) Configurations and amplitude flows are causes, and they have visible effects; they are real.
Only ratios between amplitudes are “real” in that sense, because if you multiply the amplitude of everything by, say, exp(2πi/3), nothing actually changes.
A1987dM comments on Configurations and Amplitude