> Advanced DC-coupled analogue technology offered a new high in audio performance
Read it carefully. It does not say "DC coupled everywhere". A Dynaco tube amp is DC-coupled from first stage to second stage (grid strapped to plate) but sure is not DC-coupled from jack to screw. It won't do what the DC-300 would do: hold an output DC level. (The DC-300 was intended as a bench-amp, for shaker-tables and even arbitrary-waveform power sources. Nobody in their right mind needed anything that big just to drive loudspeakers.) Maybe they found a way to DC-couple more advanced than a half-inch wire, and maybe they get high on the result. But they aren't even claiming it will pass DC, just a new high.
> Is it possible that there is room for ambiguity in what the term DC coupled actually means?
Humpty says yes. And modern marking writers make Humpty look clear.
> describe DC coupled as standing for "direct coupled"
There is also that. The concepts are related but not identical. Capacitor and inductor coupling won't pass DC. A direct connection will, but raises problems often solved by sacrificing DC amplification.
> Who in their right minds spends that sort of money on a console without getting some kind of peek ..at the bloody schematics?
You can't judge a book by its outline, or fully understand a complex schematic in realistic time. It it is any good, a large-console schematic has person-years of thought put into it. If I have the cash to buy it, I'm probably not going to have time for a detailed study and re-calculation. Consoles are bought by name and model and sound and gross specs, with demo/rental/trials on big-ticket machines. If it interfaces politely with everything in the studio, and does its job, and sounds fine, who cares if the schematic looks like an explosion in a fish-gut factory, or if they use the "wrong" model transistors? Details make the difference between "similar" machines, details too subtle to appriciate at a glance. There are some very old schematics where we can still discover subtle details.
