Hi, another advantage of Gigabit NICs ist that they're operating at full-duplex over dedicated twisted-pair lines.
In some scenarios (unintelligent ethernet hub etc) this will cause less collisions, fewer bottlenecks than just using 90s era NICs (not seldomly operating half-duplex).
So even on DOS platform with limited 16-Bit packet drivers, a Gigabit NIC would make sense here from a physical point of view.

Edited.