I see we’re on to to the pedantry again, let me rephrase:
By commonly accepted standards of research and review, it does not have a statistically significant partisan impact. Furthermore, there is no reason to expect that the greatest costs associated with universal mail-in voting are substantive enough to deter more than a handful of voters out of millions, and it is almost certainly the case that these costs are lower for the majority of voters than is possible in many other commonly used voting systems.