No, it's not the simple fact that they designed their latest lenses with the ability to be adjusted, they should have allowed for prior lenses to follow suit and allow for backwards compatibility to work with their USB docks.
Because that's
soooooo easy to do. I would imagine had it been possible, or at least practical, they would have done it. However, with the functionality allowed by the new dock, like 4 point focus fine tuning across zoom ranges, that's something that probably just isn't possible on old technology. Could they have made it so that buying a USB dock you could at least upgrade firmware? Maybe. There's a huge difference between a tech pushing a firmware change via a command line at the lab and making it so that a shmoe with a laptop can do it with a laptop
and not possibly screw it up. Anticipating that kind of engineering in lens firmware early on, particularly as a third party lens manufacturer, well, it's worth of a turban and the name "Karnac".
The fact is, that just doesn't happen that often, particularly at the level of requiring
all lenses to be updated to support a new camera. And if it is, what would be more practical from a customer relations point of view, 1) send your lenses in and we'll update them for free, or 2) buy our dock and do it yourself? I venture to guess that most photographers want nothing to do with upgrading their own firmware. Hell, I know guys who are afraid to upgrade the firmware on their Nikons and have asked me to do it.
Maybe you should have suggested it to them, or even Nikon, 10 years ago?