Probably because you've never worked in China and witnessed how development of electronics happens.
Again, Apple has a $30B+ R&D budget. They pay a huge number of suppliers very early to design and qualify backups for all components to enable a quick pivot if needed. This means a chassis suppliers for example can make "soft tools" or molds made of aluminum or silicone and test parts carved by CNC. Once Apple has confirmed the final design, they can make the steel molds. This applies to everything from the dot projector, logic board, to the chassis.
You keep assuming a $4T company has this single path with no alternative options.
This story isn't even that complicated. Apple is simply choosing between an optimistic (under display Face ID) or pessimistic (same as iPhone 17) option.