nanosecond delay functions - playing with volatile

PaulS:
Does the presence or absence of the return statement make any difference? I typically do not include a return statement in a function of type void, since it will return anyway.

I think that robtillaart has based its counting mechaninsm on the declaration of variables and the usage of return statement.
If you look at his code, every function has a different combination of variable declaration and value returned.