you're right that some suggestions are made without prior knowledge of some, let alone all of the influencing factors - and no method is perfect!
To put the counter-argument forward on behalf of those of us who do make suggestions, these are (in many cases) based on our own experience with a range of equipment which gives us a feeling of how a pickup may sound in a handful of different situations - for example how a few pickups compare in a single guitar, or a few different guitars, made of different woods, and so on. That information is useful, and at least combined with as many other people's opinions as possible begins to build up a global picture of how a pickup responds more generally. This I feel is the greatest strength of these forums.
I'm all for some degree of objectivity (even where it's subjectively defined, as here), and comparing many pickups against each other is certainly a reasonable way to get to grips with how the different pickups may react to your own equipment. A blind test as you've done is even better as it removes any preconceptions the listener has from reading other subjective opinions.
Better, perhaps, would be comparison clips that other users have made with very similar equipment, but of course these are rarely available!
I'm not outwardly bashing your idea, I think it's good, but just wanted to put it in the context of the wealth of information that is already available about BKPs here on the forums :)
Roo