Tesla build batches (same colour / trim / wheels) based on both actual and anticipated orders. They also get cancellations / delayed collections etc. So a bunch of cars get built in a batch ...
Tesla then allocate VINs to orders from that batch - normally about 2 weeks before [
the boat arrives in UK port and] available for collection
Allocation may be based on numerous factors - for example how valuable your order is - an order with FSD may score higher than one without. Transporting it to Edinburgh may tie up transport that could ferry multiple vehicles to Bluewater in the same time ... staffing levels at handover sites vs. number of people who want a collection! Could be anything ...
... could also be that human has pressed the wrong button and allocated a bunch of cars wrongly ... or that the software that does that isn't really handling the knock on effects of lockdown in Shanghai very well ... if so them the EDD will "undo/revert" at some point
Basically you need to order the most unpopular colour/trim which has been over produced and from the site that is doing the most handovers! If you figure out an algorithm for that ... keep it to yourself!
My view is that it seems a bit strange that we are getting VIN allocations in UK just now as Shipping Thread has not been able to establish that there is a boat on its way to Southampton ... but maybe there is one ...