That may be so but in my experience (work involvement in a successful legal case and campaign to save a rail service in the 1990’s) the term “ghost train” was indeed used colloquially and in the media with the same meaning as “parliamentary train”..I am a bit of a railway fan. Mostly for the architecture and infrastructure, less so with rolling stock etc.
I am not sure they are correct in those videos. They are confusing "parliamentary trains" with "ghost trains". The former actually exist and carry passengers so they are hardly ghost trains. The reason for them is self evident, if seemingly burdensome.
I always understood ghost trains were just that. Non-existent phantom trains that were scheduled into railway timetables to maximise the efficiency of the timetable.
Extra trains such as football specials, royal trains, nuclear waste trains etc can then be slotted into the "ghost" spots without rescheduling the timetables.
I spent much of my early childhood leaning on railway bridges waiting for steam trains to pass underneath. The signals would change frequently despite no trains running through them. When I asked why I was given the "ghost train" explanation.