A magnet does the same thing. An electromagnet is very similar.
What they are saying is this creates thrust with an electric field, without magnetism.
We know that can be done as well.
It does not violate conservation of energy any more than a magnet violates conservation of energy.
Let us see it use thrust to translate distance or to gain gravitational energy. It should require energy input to do that.
“The highest we have generated on a stacked system is about 10 mN,” Buhler told The Debrief. “The magnitude is not important, really, since anything above zero would work in space!” …Sure would like some independent verification. Wouldn’t you?