Well, where’s the nothing?
If there’s people, there’s not nothing. If there’s a wall, there’s not nothing. If they’re sitting there thinking and pondering something or feeling something, there’s not nothing. It qualifies as performance art or perhaps as a not-shiny mirror reflecting back at the subject, turning the subject into the object of art that is being considered in the aesthetic.
“My thoughts/feelings/emotions are the aesthetic now”.
That is the art in that style..
Nothing is a concept and thereby has properties. As soon as you name it and it’s conceptualized, it becomes something with aesthetic interest. Even nothing is art.