When and where is apply_filter called for pre_user_pass?

Greetings

The main user base for a new wordpress site is senior citizens, and after a quick user test yesterday, I found there is a huge, tremendous challenge for them to remember or copy down (hand-written in the test yesterday) the long multi-case hash password emailed out when registering.

So I have added:
add_filter(“pre_user_pass”, “myplugin_filter_pre_user_pass”)

and it is not being called. So I have dug through the user.php file and cannot find any path through the wp_insert_user where that filter is applied. FYI, my approach is to not use a hash for the plain-text password, rather a simple noun out of a list of 20 words, appended by a 3-digit number. Kinda weak password, but for the sake of creating a new user for a senior, it would be much more appropriate.

Thoughts? Help? Thanks.