Ah, Flocko, what you are not taking account of is the fact that queries about the Listener here on AnswerBank invariably ask for help with just ONE clue. (Put 'Listener' into the site search slot and you will see just how rare even these are. Listenerites would have you believe there is an avalanche of such questions.)
There is not a shred of evidence that anyone who has ever asked for such an answer - or anyone who saw it by chance (your "wide world") - has even completed the grid as a result, never mind submitted it and never-never mind won! Even if a thousand people submitted a correct grid once, as the result of an answer given here, that would have no effect whatesover on any individual Listenerite's "all-correct" status, anyway.
By comparison, two people who win by doing it in collusion each received help with EVERY clue...that amounts to several years'-worth of AnswerBank Listener-questions!
The key objection is not to the Listener, as such, but to the notion that any one prize crossword should be given protection whilst some of the very solvers of that crossword themselves seem perfectly happy to provide answers to any other prize crossword before the closing date.
Collusion is collusion is collusion, so your opening paragraph is simply wrong. I'll leave it at that.