The bigger problem is when you need a new machine fast, the apple store doesn't have anything but the base models in stock. In my org we bought a machine for a new developer who was leaving town, and were forced to buy an 8gb machine because the store didn't have other options (it was going to be a 2 week wait). As you can imagine, the machine sucked for running Docker etc and we had to sell it on facebook marketplace for a loss.
I've never encountered an actual Apple Store not having specced up machines on hand (maybe not EVERY possible configuration, but a decent selection). If you go to a non-Apple retailer, afaik, they are limited to the base spec machines (RAM wise), it's not even a matter of them being out of stock. If you want anything other than 8GB (or whatever the base amount is for that model) of RAM you need to go through Apple directly. This was the case, at least in Canada a few years ago, correct me if I'm wrong/things have changed.
