...continuing my monologue...the above code is not correct.

I decided to get into 2016 and used the available notifier instead

$zco_notifier->notify('NOTIFY_SEFU_INTERCEPT_ADMCATHREF', array(), $link, $page, $parameters, $connection);
https://www.zen-cart.com/showthread....alog_href_link

So now no modifications are necessary to html_output (catalog/admin).

These changes have been added to my Github.