Thank you for the thoughtful response. As I mentioned in my initial comment, I have already excelled in both an analytic graduate seminar taught by an NYU alum (I will have at least two more by the time I apply) and in an undergraduate logic course (including symbolic logic, which I can work through because the ideas are still ultimately verbal). I have also participated professionally in my particular AOI. The spatial processing deficit has never impacted my non-mathematical academic performance; I have performed well in the discipline, will have strong letters (the only reason they know about this is because I have brought it up for this reason; it wouldn't have become apparent to them otherwise), and have people familiar with my research in some of the departments that I am considering applying to. I caution at being arrogant, because I sincerely do not think I am more or less philosophically qualified than any other applicant, but to the degree that most applicants can be presumed to be qualified, I am in that pack minus my quantitative scoring. If I can get my score to a mediocre place, it seems from this thread that a lot of folks are saying not to worry about it too severely. But if it is a bad score, it seems as if risking disclosing might be better than risking inexplicably poor performance.
This is genuinely my concern. I have not gone through practice tests on the quantitative section at this point, but it would not surprise me at all if I hit terribly low scores such as that in the Quant. section, while hitting high percentiles in writing and verbal. Of the many, many reasons standardized admissions testing is bad, which also includes class disparities and the like, this is one of them. These tests simply don't work if you fall outside the white, middle-class, neurotypical archetype they have been built for. It doesn't mean I am not going to do everything that I humanly can; but I also know that I am not someone who can simply practice into succeeding at the GRE. There's a clear ceiling and it has nothing to do with my philosophical abilities. Concrete mathematical abilities (as opposed to understanding the logic behind math, which is separate)? Certainly. American Sign Language abilities? As I learned at a conference recently, I will never be able to learn ASL. Ability to take timed mathematics examinations? Quantifiable impact. Analytic metaethics? Not a problem (a meaningful challenge, as it ought to be for all of us, but not because of this).
I don't expect anyone here to have a clear bullet; I was just wondering if anyone might have personal experience with an ad. com or with this in their own experiences. Neurodivergence among graduate students and academics is not uncommon, so it's always worth trying.