So as a straight mod user that has no idea about lua, api, etc:

What are this mod's advantages over the Rail Tanker mod?

The only differences for the user are that this mod doesn't use dummy items to support full/empty conditions, and that it does allow tank cars stopped at signals to load/unload.

I made it for my own satisfaction, because the code in Rail Tankers is far more complex than it needs to be now, due to its age.

The feature of full/empty conditions turned out to be to useful for me to be without. Will try this mod again when/if it can support it.
Also you might want to be more clear about it not supporting full/empty conditions.
Saying "...doesn't use dummy items to support full/empty conditions" made me think that you had found some other way to support it than using dummy items.

Doesn't work afaics. The pump just acts like there's nothing there.

Yeah my pumps don't work either for some reason