Hello,
We have a setting for this; check the box to allow the vendors to apply to become a vendor and check the box to approve vendor applications manually(they become pending vendors first and you must approve them.)
wp admin > woocommerce > wc vendors
The screenshot you show here — it looks like you do not have the “approve vendor applications manually” checkbox selected. Therefore, vendors are being automatically approved.
The /my-account/ page is the best register page to use with WC Vendors, as that is the page we hook into to add the “apply to become a vendor” checkbox.