I guess it's worth pointing that when humans learn the long-horizon tasks that we learn by repetitive training, we segment them in tasks with a shorter horizon and compose them hierarchically later.
Yes the model may not be able to tackle long horizon tasks from scratch, but learn some shorter horizon skills first then learn a longer horizon by leveraging groupings of those smaller skills. Chunking like we all do.
Nobody learns how to fly a commercial airplane plane cross country as a sequence of micro hand and arm movements. We learn to pick up a ball that way when young, but learning to fly or play a sport consists of a hierarchy of learned skills and plans.