The purpose was to see what a group of folk who'd watched a lot of noir by 2005 (prior to your arrival, which was after the Great Schism and well after this vote) would come up with in comparison to other lists that were floating around at the time.
Your list above supports the notion that the films Dan listed, while all very good, are not films that are really in the top echelon. Thus, given the constriction of the ballot, it is unsurprising that most of them did not receive much support. Dan is certainly right that the "hard-boiled paradigm" was partially responsible for this, but some of it is due to the fact that "spy noirs" have a more specific context that served to separate them in people's minds from the post-war domestic melodrama with obsessive behavior, which in turn was separated from the crime dramas with desperate individuals, which was separate from the crime dramas with hardened criminals and ex-cons.
We did start, but not complete, a more ambitious year-by-year method (conducted in the fall of 2005) for ranking the films that was meant to give more films in each year a chance to be graded against their competition. Since that effort stalled after the 1949 noirs and the Great Schism occurred soon afterwards, we can't use the results for anything comprehensive--but we can look at the results in several years, which will give us a wider lens to work with than the not-nearly-granular -enough Maltin rankings.
Here are the results for 1946:
THE KILLERS, 24.4
The Big Sleep, 24.2
The Strange Love Of Martha Ivers, 20.8
The Dark Corner, 20.6
The Postman Always Rings Twice, 20.3
Black Angel, 19.6
Somewhere In The Night, 17.5
The Blue Dahlia, 16.8
The Chase, 16.0
The Stranger, 15.8
Nobody Lives Forever, 14.2
Night Editor, 12.4
Deadline At Dawn, 11.6
The Dark Mirror, 11.0
The Locket, 11.0
The Spiral Staircase, 10.1
So Dark The Night, 7.5
Strange Impersonation, 7.5
Panique (WI), 0.6
These won't quite track with the 1946 films you'll find in the Top 25 poll, but there is a fairly strong correlation. Note the position of NOTORIOUS in this poll. (And, for that matter, BLACK ANGEL, which features a "good girl" heroine.) And note that THE SPIRAL STAIRCASE, which doubtless suffered from some "noir identity" issues (at least partially due to the "hard-boiled paradigm") still drew a respectable number of votes.
The idea would have been to look at the tiers of 25 films per year and compare them across years. Each year would have a 1-5 list, a 6-10 list, and so on. You could then group each of those tiers by year and see how they shook out in comparison to the constricted Top 25 poll.
But we didn't finish that--and it was a lot to ask of any group, even one that was (for awhile, at least) extremely energetic in terms of such a project. It's certainly easier to do what you suggest, but it doesn't hold much potential for telling us much...other than Hollywood professionals were accomplished at making diverting product.
As I noted earlier, it would be an interesting exercise (at least for me) to see you take your 102 "E" grades from the Top 25 poll and try to separate them into three tiers. The advantage is that you are pretty darned systematic and you've seen all those films, which was not necessarily the case for those enthusiasts who were kind enough to indulge me back in 2005. If you feel like giving that a try, that would be great. If not, I certainly understand and (of course) no hard feelings...!