"especially when it comes to the sink or swim approach of providing no assistance to command trainees".
An initial part of command assessment is establishing if the individual has the qualities you are looking for. In very large enterprises this is a small problem as they have both time and resources to work their whey through this situation and "deferred success" can still be addressed within the same budget.
In smaller organisations , where you have both time and budget constraints, you have less time to manoeuvre and so set standards that you hope will ensure that those selected will achieve the required standard at the first or second 'hit'.
Command Training then starts after the individual has shown themselves ready for Command. Command ability cannot be taught in any kind of worthwhile command course, you cannot be taught to 'Command', you can be taught how you can best direct your innate command ability.