This comes up from time to time on SOTA threads often as an argument as to why you don’t need an ATU. It’s only true for practical antennas like dipoles if you operate in a narrow range of frequency, e.g. on 30m band. If you look at the VSWR plot for my portable 80m half-wave dipole, you would want to tune up at each end of the band if you run QRP as I do.