I believe that they're still issuing 'complete production run orders' behind the scenes, and only selling the items on the website once they arrive at the logistics warehouse — in the cases where they haven't made the item yet, they indicate 'preorder' or 'ships in X months', because cargo ships are slow and they're neither paying for air freight nor producing garments domestically. Otherwise you'd see
every retailer taking days-to-weeks to initiate a shipment after the order is placed — either it would have been marked 'preorder' (or 'out of stock' after overselling it) because you're being committed an item from a general pool that hasn't been produced yet,
or it's from in-stock inventory with JIT replenishment,
or MTO/CTO and a production-line allocation is taken aside for your order before it reaches the general pool.
I can't wait for a world where order production, inventory, shipping, and returns are all connected by electric cargo drones that fly containers back and forth using solar power — but this also highlights a critical weakness of 'globalization': when your production, retail, shipping, and returns are all colocated within the same small region, you can do JIT or MTO/CTO with a vastly simpler logistics chain. It's why Walmart sells local farmers' eggs at their stores: eggs are an incredibly annoying food to put through a logistics chain, so if you're JIT replenishment like Walmart is, you want to replenish from the closest possible source of eggs — and that's why In'n'out Burger is only in certain areas of the U.S., too, directly corresponding to whether they can get beef at their target price including transportation costs. American Apparel understood this and did relatively well on it for quite some time, until they collapsed for (checks notes) opening hundreds of retail stores using debt and filing for bankruptcy. Don't count your chickens until the eggs have hatched, indeed.
There is an unmet market niche for tailoring with the 'construct the garment from measurements' stage automated, but critically not the human in the loop during initial measurement, construction, updating one's measurements, and so forth. It was critically important when I was having a corset made to ensure that the folks making the corset took my ribcage angle into account, and they didn't have a 'standard' measurement for that, but they were able to ensure that the construction team had it accounted for. That corset cost four digits because a team of humans spent two months sewing it, and for a corset, that's not something you can currently license or build automated production for. It's a 100% CTO garment sold by a 100% CTO shop, because you cannot non-custom a perfectly-fit corset — and an imperfect fit is fine for occasional use for people in the relevant medians, but most people buying a corset are not in those medians. So, tying this back to the main point, if that shop had offered a service for "we'll also make you some shirts", I would have bought them by the truckload because they would be, bar none, the best-fitting shirts I've ever worn. They didn't, because their production capacity was both hyperspecialized and limited, which is fine. But considering mechanical automation lines versus where to use human beings for their competences, I think one hour per few years of labor paid to someone to measure me and make sure they get it right, plus the cost of the machine-production time for the garments, would be world-changing.
Even if the garments are machine-printed and machine-cut and then machine-assisted sewn by humans, building out the CTO logistics backend of Apple's computer ordering processes, combined with an in-person competent human tailor to translate "my concerns" into "less stretch, more structure" and a production team to translate "more structure" into "use a more complex dart structure and use the -5% stretch fabric"? It wouldn't be hand-sewn, but it would fit, and that would devastate a great deal of business that today is grudgingly conceded to hourglass-exclusive retailers where no alternative yet exists.