I'm probably at least 3 months away from receiving mine but, for what it's worth, I have an MTO order under construction that specifies a fitting adjustment to the left shoe (written up on the order sheet by Dean as "1/8 heel lift - l/foot only"). My adjustment was due to the fact that the back of the left shoe was flopping around a bit as I walked whereas my right heel was staying nicely anchored in the heel cup (is that the right term - "heel cup" that is, not "flopping around"?).
I had a meeting with Dean in the Savile Row store so we could discuss any issues with the fit in person. I'm not sure how MedTech determined the correct fit adjustment if he didn't have an in-person fitting (maybe he did) but the basic message here is that when going MTO there are at least some adjustments that can be made for specific customers in order to optimise the fit as evidenced by both MedTech and myself.