I have considered these myself, but note that it has a grounding prong, that means you can only use one of these in a duplex plug, in the bottom plug (assuming your duplex plugs have the ground prong at the bottom), because the grounding prong forces it to be mounted in one direction only.
However, the specs (and reviews) indicate that the grounding prong is not actually electrically part of the circuit (“3-prong (NOT Grounded) design”), so someone in the reviews has suggested that you can tear out the grounding prong with pliers without affecting its functionality, and then you might be able to use two in a duplex plug - one pointed up and the other pointed down.
The dimensions make it appear that the prongs are located close enough to the top end to allow a second one to be plugged in upside down above it (if the grounding prong is removed), but the “pictures” are not real photos (they are digital renderings), and it is difficult to determine from these fake photos, and from the dimensions and the location of the prongs, if it might block the ability to place a second one upside down in the other duplex plug.
On power output, notice that they say it is a 12W max output. At 5 volts, that is 2.4A max. It is unclear whether that 12W is per USB port, or overall. But the specs also indicate "3.1A max, up to 2.4A per port", which essentially means that you will have roughly 1.5A per port with 2 (identical) devices plugged in.
From other discussions in the forums about the V3, it seems that we need to supply each V3 with 1A, and maybe a little more if running longer than normal cords. So it seems if this will provide 1.5A per USB port, that seems like it would be enough to use a longer than normal cable.
I’ve been trying to find something equivalent, that only has 2 prongs in the first place, with dimensions that will allow 2 to be plugged into a duplex plug, and that will provide a bit over 1A per USB port (at 5V). There are several other dual power adapters available on Amazon with 2 prongs, some with foldable prongs, some with fixed prongs, and they all look like they do not have “polarized” prongs, so they could be used in either direction (up or down). But I have not gotten around to trying any to see if they will provide enough amps and voltage for longer cables, and to see if their dimensions and prong positions will allow two to be used in the same duplex plug.