All of your examples are schematics.
There is no hard and fast rule that determines the how/what/why of a one-line drawing. The basic concept behind a "one-line drawing" is "minimalism". That is, using one-line to represent many lines.
A true "one-line drawing" is used to provide a general indication of the relationship between the various aspects or components of a process or system.
If you have a physical module sitting "here", and another physical module sitting "there", and let's say there are 100 wires between the two modules... you can present the information in a few different ways...
TYPE-1:
You can draw each wire between the two modules, indicating the identity of the wire and the appropriate connection point on each of the modules. That would be a full blown, wire/connection, schematic... at least in terms of the connections between the two modules. It might, or might not, provide the internal circuitry in the modules.
TYPE-2:
You can make a drawing that identifies each wire and connection point at the connector of one module, then compress ALL of those individual lines into one single line. It would look as if all of the individual conductors were all part of a single cable... which might, or might not, be true. You then carry that one-line to the destination. At the destination, you break-out all of the individual conductors, show their identities and connection points.
Along the way, other "one-lines" might join, or leave, the original one-line. In automotive wiring, this would be representative of a wiring harness. The content of those "one-lines" joining or leaving is not known at that point. You would have to follow the "joiner" back to its' source to determine the content. You would have to follow the "leaver" to its' destination to determine its' content.
That technique helps to keep the "clutter-factor" down. There is a great advantage in having the appropriate amount of "white-space" in a schematic, a drawing, text, whatever. It simply makes it easier to read. Type-2 is not a classical "one-line drawing".
TYPE-3:
Then there is the true "one-line drawing". While it is conceptually helpful, in general, it is technically useless. These are generally used to provide a general description of the concept. It could be used in terms of hardware, software, or...
In the case of a true "one-line drawing", there would be a single line between the modules indicating only that there is a connection of some sort between the two modules. This is the kind of drawing that someone would bang out on a napkin while having a beer at the bar... very few details, if any, only the general indication of a connection.
As in Type-2, along the way, other "one-lines" might join, or leave, the original one-line. However, in this case, the content of the "joiners" and "leavers" is simply not known. All you know is that there is a connection of some sort that involves other modules.
Power Distribution Drawings generally fall under Type-2.
Detailed cable connections fall under Type-1 or Type-2.
General cable connections fall under Type-3.
Modern automobile electrical schematics show up in all three types.