flyspell-correct-word-before-point vs ispell-complete-word

[Lennart Borgman (gmail)]

Just out of curiosity I tested ispell-complete-word. It did not work for 
me (using aspell from cygwin). It looks like it is trying to use grep to 
search some dictionaries that are not there.

In contrast flyspell-correct-word-before-point works.

What is wrong with ispell-complete-word, is it just missing/misnamed 
dictionaries or is it some kind of "left-over"?