Yes, it is ... but, it's also used a lot when Pushing double rigged jigs. It "could" be used for casting, but the weight would be considerably smaller in most instances.
IMHO .... the idea is to present more baits/colors & cover a wider range of water depth, with the intention of possibly catching two fish at one time. I fished this way once, with a member buddy, and out of the 100+ keeper fish that were caught, a double on one rod occurred only once (that I remember). In fact, whenever the double rigs got snagged & lost a jig (or the whole rig) we kept fishing with a single jig on that rod, and still got just as many hits. And, in almost 95% of the cases, the fish hit the bottom jig, anyway.