Definitely not, although the airline wants you to think so. NW is the king of so-called "unscheduled" aircraft changes at hubs for through (XXX-MSP-XXX, etc.) flight numbers. Not only is the flight marketed as through, same-plane service when they don't actually operate it that way, but if the first segment of the flight gets delayed, the second will generally take off on time. This brings extra happiness to those folks who booked a "direct" two-segment flight and assume they couldn't possibly "miss the connection." Oh yes they can.

It's a fundamentally dishonest marketing practice.