The trouble with long-winded text descriptions of systems logic - in FCOMs and elsewhere, including PPRuNe - is that the "AND" gates and "OR" gates can so easily become confused by the often unavoidable limitations of syntax, grammar and punctuation. That's why design engineers comunicate their proposals and requirements by mathematics or logic diagrams, I believe.
Bill Smith has given us the best analysis so far, and certainly in line with my fading memory of the A320.
There's just one other point about the desirability of selecting reverse idle, in preference to forward idle, which has not been mentioned. Although these fan-only reversers are fairly ineffectual, in comparison with the old-fashioned buckets of my youth, what is sometimes forgotten is that they do at least eliminate the forward-idle thrust that helped the Iberia A340-600 overrun the runway at Quito recently. [Yes, it was also stuck in flight-idle, instead of ground-idle.]