House tracks

I think your "corruption theory" is probably pretty good. Railroad terminology in the real world was not necessarily all that precise, since nobody referred to a dictionary when they were learning this stuff. Meaning was usually inferred from the context. Since a lot of freight houses disappearred over the years, the use of house track became quite imprecise in my experience.
As John Bush mentioned, a "house" track was typically a track off of the mainline or siding that allowed cars to be set out without blocking tracks used for the meeting and passing of trains.
In the old days a lot had actual freight houses, in more recent years a team track kind of operation was more typical, or just a place to put compnay equipment or bad orders.
As best as I can tell, the track at Cumbres was always a siding used for the meeting and passing of trains. What made it a bit unusual was the placement of the station between the siding and the mainline (which would indeed be more typical had the siding been a "house" track). Perhaps there is some history here that can clarify why the layout was this way.
JBW