We worked with one of those machines making step-in snowboard boots with Technica. The first one I saw was in a huge former state run shoe factory in Slovakia making massive quantities of original model Addidas shoes that made a comeback in the mid 90’s. They had pulled the original tools out after being shelved for decades.
The upper gets fit over a last, the mold closes around it and a double injection is made. Can be a solid injection combined with a foamed material. In our case a rubber sole was sealed into the mold and the “foam” injected between the sewn upper and the contact sole, also encasing a metal frame for binding connection, then the flange between trimmed off.
Years later a sample is in my office, the foam has really deteriorated over time it has totally lost all elasticity and crumbles like sand with a fingernail.
It is a cool process, but the slow rate of cure requires a turntable of multiple molds in order to make commercial sense. Great for committing to runs of tens or hundreds of thousands of pairs, not so great for developing something that needs to be iterated and evolved.