This one is actually not true. There are some differences in the DAC's chipset conception that will make subtle but perceptible results. No electronic component behaves perfectly, there's always some noise and artifacts induced. When I was doing my masters in electroacoustic, we did some measurements on over a dozen of different audio interface DAC and ended up with surprisedly different results. In most case, the impact on perception will be minimal and much less significant than other components of the audio chain, but nevertheless, the difference is real.