I have a suspicion he means a runner who neither lands on his heel, nor toes, somewhere in between. At first I thought he meant neither a supinator nor a pronator.
OP, in my running days they use to recommend keeping two different kinds of shoes and alternating. Maybe things have changed a lot since then. I remember the Nike Vortex being a pretty light shoe, and another even lighter one I loved which was sort of pink, possible used by some for racing.
"Epic" was a heavy horrible shoe, Nike's first 100 dollar shoe.
Running over the same old ground ... shorter of breath and one day closer to death.