The question of what's logical in a lowest logical airfare policy has always had more than one answer. There's much more now for program managers to think about than when such policies came into vogue in the late 1990s.
In general, the lowest logical airfare is the cheapest available at the time of booking that abides by corporate policies without causing undue inconvenience or discomfort. One traditional consideration relates to whether companies insist travelers book a connecting itinerary if it's much cheaper than a nonstop. Others are about booking windows, alternate airports and dollar thresholds. Some lowest . . .