Calculate Current Regulation - DRV8825
The answer is yes, accuracy can be degraded. The test engineers at TI left you that note to let you know that if you operate the VREF below 1V then the circuit will not preform like the equation that they provided. This is probably because they didn't put a super accurate opamp\comparator in silicon to measure the current (in figure 6) and it has some kind of common mode range or offset.