Moin!
I don't know, what is '20th-century' with the Zeiss DSF??
Let me try to explain
Basically, when I start adjusting focus, I do know whether I need fast or slow adjustment, but the scope doesn't.
With the Zeiss System as I understand it (and please correct me if I'm wrong), whatever I actually want, I get "slow" at first. After turning the slow knob for a while, the scope, still not knowing what I want, kicks me to "fast".
This is infallibly either late, if I actually wanted "fast", or wrong, if I wanted "slow".
That's a hardware-only system incapable of processing the information required for correctly addressing the task at hand ... 20th century, Meccano kit technology.
Not to say I'd be happier with a millenial-style "auto focus on smiling bird" app running on my scope, but you get the idea ;-)
I've heared that some people don't like the DSF, that's a cognitive problem in my opinion.
I'll readily admit that it has a cognitive aspect. I'll still maintain that the system has objective shortcomings, but I'm aware that many people just get used to it and maybe find something positive about it (as in some situations, it's admittedly faster than single-knob only).
Personally, I'm not very good at "just getting used to it". That's a cognitive thing for sure, quite inconvenient for myself at times, but it also drives the innovative "Tüftler" side of me ...
Regards,
Henning