Back when Sir Ralph was writing, anything smaller than a 12 was pretty much a toy. But a modern smallbore is a very different tool, and modern ammunition is also significantly better. We need to remember that what we think of as the modern 12 didn't really evolve until the 1920's, with the advent of the Super-X load.
As far as driven game goes, back when Sir Ralph wrote, those birds were not particularly long shots. Mostly under 30 yards. The mania for really tall driven birds is a relatively modern phenomenon.
If the first shot is long, you take it with the tight barrel (assuming double triggers). If you wound the bird, you still follow up with the open barrel. You might get lucky and hit the head, break a wing, or otherwise put a pellet somewhere vital. If you're assuming that your first shots are always going to be long, then you should set yourself up with tight chokes in both barrels. But I'd rather set myself up with more open chokes in both barrels, because I've found that I don't often take a first shot beyond 30 yards. Shooters are well advised to prepare for the shots they actually get most often, and are capable of making.
