From what I've read and understand the flow of electrical current is caused by electrons that flow negative to positive. The steps for jump starting a vehicle and why it's recommended to disconnect the negative battery terminal before working on them, never really made sense to me until I looked up "Electron Current" vs. "Conventional Current"
Electron current vs conventional current has no effect on disconnecting the negative first. On a positive ground system you would want to disconnect the positive first.
On a negative ground system, the whole body of the vehicle is used as part of the ground circuit. If you put a wrench on the positive post and accidentally touch the body, it arcs. If you put a wrench on the negative post and accidentally touch the body, it does nothing. Once you remove the negative terminal, the positive post is then safe.
Electron vs conventional current is not really a thing. Current only flows from negative to positive. Wiring schematics are drawn from positive to negative. Why? Because we figured out how to get electricity to work for us before we understood how it worked. It's a convention that needs to die, but engineers are too set on drawing diagrams from positive to negative.
When I was learning how to work on a specific generator for the Air Force, we learned the wiring schematic. The switch & relay-controlled system had one component tray with circuit cards for faults. I think there were five transistors in the whole generator. As we were learning the schematic, the instructor was following the path of "potential" through the circuit, and as soon as he hit the transistors he started talking about "current" and reversed the direction he was tracing. He lost everyone in the class, but he was instructed that he had to teach it that way.
Wiring schematics should absolutely be drawn from negative to positive. Wiring diagrams show the actual wire location and connection, and still need to be laid out in the conventional manner.
