Well I am sure they have done Industrial Engineering studies on production line throughput (pretty standard stuff), but the adjustment factors for unknown unknowns is the wildcard (supply chain issues, labor shortages, other COVID impacts, etc.).
I agree that in "Normal" times they would have the mass production expertise and historical experience to make legitimate estimates. But these days? The IFs from every source are backed up with more IFs. It's so hard for a supplier to make guarantees that THEY can't make because they have supply chain issues as well.
Agreed, thankfully the flexible manufacturing center approach Ford is taking with the new factory could help mitigate this to an extent (if used correctly), by letting them resequence operations on the fly to temporarily skip missing parts and install them later. Ford should be using the time between now and Job 1 to figure out and test these contingency plans so they can enact them with little to no delay as needed.
