I think the article puts forward one point - if the number of devices using DC is large enough, the load will become much less variable. Less variable loads mean one power supply can operate at peak efficiency rather than having many sitting idle most of the time.

I'm not completely convinced that this makes sense though. Any low voltage DC distribution network will need fairly thick wires to distribute anything but trivial power levels. The power lost in the cables over tens or hundreds of feet would probably make any efficiency gains fairly moot. The efficiency of modern switched mode power supplies is fairly high, and my understanding is that the no-load power use is almost trivial (milliamps).

One issue that seems to have surfaced recently is that there's loads of very, very cheap AC-DC power supplies which are awfully made. It would definitely make sense for a single high quality supply over a bunch of cheap, noisy and dangerous ones, but I think the best solution is investing slightly in wall-socket based power supplies of a known quality.

As an aside, power transmission with DC is actually quite a lot more efficient than AC. The reason AC won the power race was the ease of voltage change with transformers. As solid state power electronics improves, we're going to see more and more DC based transmission lines. We're probably centuries away from a DC grid (if ever).