I looked into the VIN assignment process/procedure/regulation extensively in my obsession with waiting to be told my VIN by Tesla (i.e. VIN assigned to car, not us people being finally told by Tesla the VIN of the Model 3 we are buying). I found a lot of the same language you and others have found. I also searched Model S and Model X forums for how the VIN process worked for those owners (who were equally obsessive about waiting for their vehicles).
From a government regulation standpoint, a large manufacturer like Tesla has to apply for VINs before the cars are manufactured. As we have seen they do so in batches and really only have to say very little about the specs of the cars they plan to manufacture with those VINs (thus the ability to identify how many Dual Motor VINs they have applied for). Most other manufacturers it seems assign a VIN to a chassis as soon as that chassis is assembled in the manufacturing process. Tesla does this too. Prior to that point, the VINs are on a list and they do not have to be manufactured in VIN order. It seems that Tesla has pre-assigned sets of VINs by configuration/color, but they do not seem to be building them in that same order (thus why we see owners being given VINs for the same colors on the same dates in totally different ranges). Tesla seems to know VIN XXXX to VIN XXXX will be White/Sport or White/Aero or Black or Blue or whatever. Then it builds those vehicles with those preassigned VINs as needed (pulling from the lists of unused VINs as needed). Yes, some vehicles could have been built, had a quality issue, been sent back to have something fixed or redone and that could be partially why an earlier VIN shows up later (this happens all the time with all manufacturers though, the key is that vehicles just need to pass all quality standards before being assigned to owners). Keep in mind that we see gaps in VINs being reported on the Google Sheet and in these forums, but our data is only a sampling of the total number of vehicles manufactured and delivered.
Model S and Model X owners got their VINs when their vehicles were about to or just hit the production line. Nearly all of those vehicles though were custom orders. The Model 3s are not custom orders. They are inventory vehicles that are built, then once ready to ship the owner is informed of their VIN for their vehicle.
