It depends on where you are from, I guess. If the object is placed between the wheel and the hub, it’s a wheel spacer as it allows for different back spaced wheels to be used on a car that otherwise wouldn’t/couldn’t use said wheels. The only time I have ever heard anything even remotely close to “engine spacer” is when modified or custom engine mounts allow for an alternate placement of the engine within the engine bay. Bell housing spacers do the same thing for the transmission.
Why would you call something an “engine spacer” if it has nothing to do with placement of the engine?
Wider track from spacers.
I know you get it but others may not.
Offset at zero is middle of wheel/bolt face is dead center of wheel.
Moving bolt face toward inside of wheel is called positive offset, so rim looks deeper.
Moving bolt face toward outside of wheel is called negative offset, so rim looks less deep.