Language is funny like that. Terms which can be seemingly imprecise or technically inconsistent can still serve to communicate an idea when taken in context. Playing 'gotcha' semantic games rarely serves to move the discussion forward.
Many large buildings have, as part of their mechanical systems, tanks which maintain extremely low air pressures. (Car brakes use a similar concept.) These are often referred to as "vacuum reservoirs". I once teased an undeserving young plumber's helper who was working on such a device by asking him what, exactly, was being stored in the tank. "Vacuum." he replied with a puzzled expression. "But what
is "vacuum?", I then asked. "Isn't it the absence of anything?". "Well, ...

". "So what you've got there is a tank full of nothing." Which it was, of course. Sort of.
Yeah. I was being a smart-ass.
I understood what Scrut meant. I'm pretty sure you did too.