parsePatchLevelValue silently synthesized day=01 when input was 6 chars (YYYY-MM) and caller wanted 8-digit YYYYMMDD. If ro.vendor.build.security_patch ever returns YYYY-MM on a target device (older Samsung firmware does), the synthesized day disagrees with the real bulletin day -- a detection fingerprint. Return null so getRealDevicePatchLevelInt falls through to Build.VERSION.SECURITY_PATCH, which is always YYYY-MM-DD.