Thanks for clarifying.
So, it seems that the WooCommerce login form is not using the standard WordPress login_form
hook, but instead using its own woocommerce_login_form
hook, with a slightly different form as well. This is particularly strange because Automattic (the company that makes WordPress) also acquired and now maintains WooCommerce.
Nevertheless, after a fair bit of fiddling, version 1.2.1 implements the reCaptcha on the customer login form. It was already implemented on the common login checking back-end, but failing in the case of the WooCommerce form.
So, again, there was inconsistency between the two front-ends behaving differently but both of them relying on a common back-end. Pretty weird.
Please do check out 1.2.1 and let me know if it resolves the issue for you. It has resolved it on my own client websites (though it seems nobody has tried to log in to their customer account since 1.2, or we would have heard from them).
Thanks again for the clear explanation, and here’s hoping it’s resolved now!
-R