Just so that American readers who are not familiar with traveling English tailors are not confused: the single forward fitting for commissions after the first is not peculiar to A&S or A&S expats, but quite common among all the SR houses for their clients in the United States. It's a predictable adaptation to serving customers efficiently across an ocean, and because the relationship of SR tailors to American customers stretches all the way back to the age of ocean liner travel, it's a habit arising from the need to deal with the historically high cost and difficulty of travel during the past century.
It does not have to be that way today, perhaps, with cheap air travel, and there are exceptions, but you will find this to be a widespread practice.
At A&S, however, it might be the case that fewer fittings became a point of pride (or expediency) even for local customers.
The question that interests me is: if you use a tailor who does not travel, but to whom you travel (and thus, is generally local), that tailor's style of work might never need to adapt to the single fitting model. There's no reason to be good at doing things in one go. You can fuss with things, which can be time well spent, or time uselessly spent: progress or just Brownian motion.
So, is it possible that those who do things in one fitting, customer after customer, become quite good at that? Manton has already commented that in his experience, the ability of these A&S-trained guys to get the balance right from the get go is uncanny. Or, is that type of expertise only going to go so far?
Also to be considered, and this is where I think the expats might shine more than their former home, is that even in the one fitting model, as long as the tailor is happy and willing to deal with subsequent adjustments, I would think that this is a reasonable safety valve for at least those sets of adjustments (limited, of course) that are still posssible after the garment is finished. People (perhaps people with no direct experience, so there might be a bit of exaggeration, but still...) often associate a bit of unresponsiveness with A&S on making post-delivery adjustments.
My experience has been that I have not needed more than one structural fitting with my DeBoise items after the first piece he did for me. I'm relatively particular...although maybe not as much as some of you.