I pulled the TL numbers from the paper and came up with an STC rating of around 31dB for the 20mm hole model. That is roughly the same STC rating as a decent dual pane window.
It's not terrible, it's certainly impressive that they achieved that level of isolation with holes in it. Windows designed for high sound isolation will have STC ratings in the 40-48ish range. An STC increase of 10 equates to half as much sound passing through (as a human perceives it anyway).
As for the air passage, I'm curious about the real world flow numbers.
Just an off the cuff guess: it seems like the core principle is based on resonant cavities which I think would result in higher air pressure in the cavity than inside or outside the window. In a setup like that with calm ambient conditions I wouldn't think much air would actually pass through the panels, the higher pressure in the cavity would act as a bit of a wall. In windy conditions I would imagine much more air would pass through, but I bet there would be a corresponding decrease in sound isolation as air blasting through the cavity wouldn't be able to dissipate as much energy.