Forum OpenACS Development: Re: Request for a new acs-subsite parameter
forgotten_pwd_urlis computed via the function
auth::password::get_forgotten_url, which is conceptually correct, since password recover depends on the authorities (maybe, there is no way to recover the password via web interface for some authority). This code has not changed at least since the release of OpenACS 5.0  (2004, more than 13 years ago).
However, there is similar code in the function
register/recover-password is e.g. used, when e.g. the authority returns no other URL.
What do you actually want to achieve? Tailor the appearance of the page for recovering the password? or point to a completely different page? In the latter case, you should consider defining your own authority.