Not necessarily. I believe a lot of games simply use a set of heuristics to check for unwinnable situations after generating a scenario. These are usually based

Not necessarily. I believe a lot of games simply use a set of heuristics to check for unwinnable situations after generating a scenario. These are usually based on unwinnable states that play testers have encountered, so there is no guarantee that they are exhaustive, and most procedurally generated games have a small chance to produce an unwinnable scenario.