But they don't even solve that problem! In both shops that I use (rosebikes.fr and decathlon.fr) stocks are explicitly marked as approximate, with a very visible warning in red when the stock is 2 or 1 items, asking you to call the shop to verify stock. Website is slow as molasses still.
In those particular cases then yeah, it might be a sloppy job, but you didn't made it sound like that initially, instead let us believe you meant it generally speaking