Never heard of pouring it in the carb, but I have heard of doing that with water.
Just water that I've used with a mist bottle....
I wonder if it's similar in practice as this? When I worked at Acura, some of the '91 Legends had some carbon build up due to the design of the rings and would cause knocking. The treament for this as a first step was to let the engine "drink" engine cleaner through one of the vacuum hoses. As soon as the can was empty, you shut down the engine then let it soak in for a couple of hours.
After that came the fun part! You start the car and immediately get out on the road and get the engine in the higher RPMS so as to clear out the cleaner. It made a huge cloud of smoke! We always pretended to be the Batmobile throwing out a smke screen!
If the knocking was still there, it was re-ring time....