Three days away rather than eight months. Close enough that mistakes are survivable — which is the definition of a place to learn.
The Moon is in most respects harsher than Mars: no atmosphere at all, a fortnight of darkness at most latitudes, temperature swings of hundreds of degrees, and abrasive dust that damages seals, lungs and optics. Water ice is thought to exist in permanently shadowed polar craters, and that possibility is why the poles matter.
But it has the one property Mars cannot offer: proximity. Communication is effectively immediate. Return is measured in days. A failure there is a lesson rather than a funeral.
This is why I think of the Moon as apprenticeship, in the older sense of the word — a period of formation under conditions where the master can still intervene. What would be learned there is only partly technical. The harder curriculum is the one this book has been describing.