...and they build them to order?
Exactly. Expecting stacks of product languishing in some dank warehouse waiting for an order to set them free is so 30+ years ago.
To get a superb overview of modern manufacturing and how most products that have options--like Macbook Pros-- are made in the computer age, please find James May's three-part documentary, "Building Cars," (2015). In the US, it is on Amazon Prime Video. Don't know about the UK but it is a BBC production.
In addition to world-wide shipping bottlenecks, many manufacturing fields have trouble finding enough people post-COVID to staff positions that require the human touch. Add in the fact that the Macbook Pro-M1Max is a relatively new product and those are always in high demand. You get a perfect storm.
Please see the video. It is an excellent learning tool that shows that, in many industries, giant finished goods warehouses are history.