When I was in college, we would take a "J-term" in January, where we took only one class but would do multiple class sessions per day. Like maybe lecture in the morning, lunch, then come back for lab, and then work sessions / break out discussion in the evening. Squeezed a full semester class into the month. Obviously this is not easy or perhaps even possible as an adult learner with a job, kids, responsibilities, etc. If there was some subject for which I absolutely had to quickly develop proficiency, I'd set up some kind of a focused schedule like that - lay out a curriculum plan, set aside scheduled time each day, set an end-date by which you can assess your progress.
No, though you are correct that this kind of thing is popular at small liberal arts colleges. I think the one local to me does "May term" instead. It's really a nice way to do things - I took AI one year, poly sci another, good time for a study abroad. But it's also a good way to structure the kind of focused learning the original poster queried.
