Its original use dates to WWII and was more akin to "military R&D engineer/technician": the people who developed radar, for example; or Barnes Wallis of the bouncing bomb and Lancaster bomber.
The use has generalised over time and would certainly include madcap inventors like Doc Brown from Back to the Future, who is very much not an ivory tower dweller. I would guess that that's the sense which was contrasted with engineers in the documentary.
In the vernacular of The Register, which the headline comes from, it is used quite generally for scientists or engineers.