You use stuff when it's relevant and applicable and not by applying various "century" flags.

Reinventing past mistakes in new mediums does not count as innovation.

Fair point. I'm not sure how I'd feel about it being entirely pop-up window based, which I presume is the alternative to MDI.

There is no need for pop-up windows nor MDI, it's a technical demo for the sake of a technical demo. It's no accident that the default layout contains no overlapping "windows".