String value for "has_archive" not respected

[JacobDB]

I'm trying to use a custom slug for the archive as compared to the singles (i.e. "contractors" for the archive and "contractor" for the singles), but when I set a string value to has_archive, it's not being respected. I've flushed permalinks after making this change. Is this something I'm doing wrong, or an issue with this library?

register_extended_post_type("contractor", [
    "has_archive" => "contractors",
    "menu_icon"   => "dashicons-location",
    "supports"    => [
        "title",
        "thumbnail",
        "revisions",
    ],
],
[
    "plural"   => __("Contractors", "fcai"),
    "singular" => __("Contractor", "fcai"),
    "slug"     => "contractor",
]);

References:

• https://wordpress.stackexchange.com/a/318139/24566
• https://developer.wordpress.org/reference/functions/register_post_type/#has_archive

[JacobDB]

It does actually seem to be working when I retrieve it via get_post_type_archive_link("contractor"), but even after saving permalinks multiple times it still 404s