To be fair, proper ISO 8601 specifies hyphens as the separator between date elements, and I don’t think I’ve ever seen a XXXX-XX-XX (with hyphens) be used for YYYY-DD-MM. Just XX-XX could perhaps be ambiguous, but fortunately that’s not allowed by the standard, and anyone using just year-day for XXXX-XX is absolutely trolling. YYYY-DDD could have a use, though should really use a separate separator to not sort together IMO. A year-week designation could possibly look like XXXX-XX, but that seems unlikely to just be dropped in that format without context, at least to my western US sensibilities.
Re post text: For context, Washington state is mail-only voting, so that number would (I assume) be for all votes, not just specifically requested mail-ins. I didn’t see it in the article, but I wonder if that is predominantly “centralized” or “distributed” in nature; i.e. are technically-valid ballots from all voters being incorrectly rejected by the county elections facilities office at different rates across racial lines, or are there other factors like targeted disinformation, education, local infrastructure, or socioeconomics that disproportionately affect Black (or other types of minority) voters that would make them more likely to produce a technically-invalid ballot?
Those might get the same statistic, but would seem to indicate very different sorts of problems and approaches.