menu_order, pages, default behavior buggy?

I’m trying to sort one particular sub-sub menu from my navigation (which uses wp_list_pages function with sort_column=menu_order for all the other items at every other level) alphabetically, as in A to Z.

My understanding is that if every sub-sub page has a value of zero, then it uses the page title to sort alphabetically – but it doesn’t. Even if I use the numbers 1-26 to correspond to the letters A through Z, they will SORT into alpha groups, but within are NOT sorted by any logical means.

I therefore end up with something like:

Healthy East Chicago
Holy Trinity
Health Visions

when it ought to be:

Health Visions
Healthy East Chicago
Holy Trinity

I cannot give the URL as it is behind development authentication, but my navigation menu uses:

<?php wp_list_pages('title_li=&sort_column=menu_order&exclude=24,28,292,300,329,330,331,343,344,346,380'); ?>

and it all works as expected EXCEPT for this weird glitch with sorting alphabetically. I guess I could redo everything, creating a “letter” category and putting the pages into those, but that’s a 4th level and seems ridiculously unnecessary… as what I READ in the docs for list pages seems to NOT be what is happening.

Ideas?