I doubt that is has anything to do with technical reasons. It is more their mindset that thrives on keynotes and fantastical product updates that people are scrambling to gobble up.
Apple likes to create suspension and 'building up demand'.
This works well for intimate customer products like phones and watches. Not so much for bread and butter products that people need to get some work done (like silly old computers)...
I think your conclusion is more of a subjective on opinion Apple building suspense than it is a factual reason why they have the site down for six hours. But Only Apple knows that reason, other Than speculation.