I've got a chip hold, but sitting in a parking lot doesn't bother me. My Mach E sat in a parking lot in Mexico City (Cuautitlan, actually) from the last week of October to the first week of March before it was delivered to me. And yes, they can get winter hail there (I've lived there an experienced it myself).
Ford has hundreds of procedures for things like this, and while the duration is rare, the need to performing rework, delaying certain units, and so on isn't new at all. There's a huge procedure just for selecting storage locations. Another for the actual storage. Procedures for removing from storage. And rework almost never occurs on the assembly line. There are dedicated rework employees that do anything from correcting fuel leaks caught on the line, to troubleshooting non-functioning turn signals.
The first time through rate (units shipped right of the line that are perfect) is never 100% for any manufacturer. There's always something to be corrected, and the product isn't any less new even if someone had to yank out the instrument panel offline in order to replace a diverter door, for example. If you've ever purchased another new cars, there's a non-zero chance that rework was performed at the factory.
Bigger issues ("campaigns") might draft the non-dedicated rework employs to help out. They'll be trained, but usually help out in the non-specialized roles, like moving vehicles, putting them on lifts if necessary, performing checklists, etc. Whoever actually performs the repair will be qualified to perform the repair, no doubt.
As for mileage, your warranty starts with the number on the odometer. You're not really losing anything if there are more than 10 miles on the odometer. I've twice taken delivery of vehicles that had significant miles on them; in both cases there was a note from the factory indicating that they were selected for random testing (there are small versions of test tracks at nearly every auto final assembly factory). The Bonneville and the Mustang both had less than 100 miles on them when delivered.
I'm irritated with the wait, but I have zero doubts that I'm going to get a brand new Expedition that meets all of the criteria for being "brand new" when it's delivered. And I'm picky as hell, because I help build these things for a living.