Just a guess here but I imagine that these dimmers are intended for small shows, such as bands or for DJ use where you have a small number of fixtures on either side of the stage.
I would imagine that you can simply split your L + R sides at the dimmer, rather than having to use adaptors or piggy back your lights.
Up until recently, I use to run a loom out of my 4Ch dimmer for use of DJ shows into one of my lighting bars and then another from that lighting bar into the second bar.
It worked well and especially on shows where we were set up off to one side. However, when the lights were on wither side of us, it meant that you doubled back on your cable.
I have a added a pic of the panel I made for the back of my lighting rack. This is a 6RU rack that has a 4channel dimmer/chaser unit and a 6 channelswitch pack.
The three banks of rectangular connectors are Wieland plugs which are the standard for 4 channel looms in Australia (our lighting bars are 4 not 6). The top two are for the lights and are wired in parallel, so that I can either use one to power up both lighting bars (daisy chain) or I can run one bar from each.
By having two outlets per channel, you can simply run one to the left and the other to the right, which means less cable.
Like I said, that is my guess but having worked with small channel dimmers a lot over the years, I think that would be the case.
I imagine that this is how the dimmer you are talking about works.
For those interested – the bottom Wieland connector is wired in parallel to the first 4 single phase 10A outlets and are for channels 1 to 4 on the switch pack. The other two are channels 5 and 6. The Wieland connectorloom allows me to run 4 items from a remote location. The jack input is for the audio trigger for the chaser and the large black connector is power in. This was taken just after I had built it and before it was labelled and installed.