If you try plugging in TWO 120 volt from the same room they could be on different phase,
creating a dead short, and trip breakers smoke wire etc. And 120 will use more watts than 240.
There are two PSUs in the unit, and it should be perfectly fine to run them on separate legs of a residential service.
Not to mention he is completely wrong. Why do so many people pretend to understand how household power works when they have no clue??
240 will be more efficient, and if you have the ability to run 240 legs to the area you want your miners, do it. Building a consumer device that uses more power than a 110 outlet can provide is fairly stupid, but it seems like they had no idea how much power it would end up using.