Sorting WP user columns by non-meta value (PHP) - php

Question

UPDATE: I've read a few more posts about similar issues and the consensus seemed to be that filtering by the actual data in the user admin table isn't an option, and that sorting needs to be done via adding the data to postmeta if it isn't there already. Hoping this isn't the case, but it's starting to sound like it.
I have added a handful of custom columns to the user admin table. Some of the columns get their values from custom user meta, but some do not. I've been able to make the columns that source their content from meta just fine with
if ( 'member_number' == $query->get( 'orderby' )) {
$query->set( 'orderby', 'meta_value' );
$query->set( 'meta_key', 'number' );
}
...but the column I'm unable to sort a column that gets its values by cross-referencing the user's info against entries from a Gravity Form, sorting the GF entries by date, and outputting the position of the GF entry that was matched to the user.
It might be simpler to just say that I want to display a "wait-list position" that can change frequently and would require updating postmeta of ~100 posts on a regular basis to accurately display the users position in the queue. Not thinking that was practical to do, the best I could come up with is to reference the user's email address against the list of those on the wait-list.
If it helps, the code that references my custom function and applies it to my column is:
if ('waitlist_pos' == $column_name){
$waitlistNumber = get_waitlist_position( $user_id );
$value = $waitlistNumber;
return $value;
}
...and my function to get those values is:
function get_waitlist_position( $user_id ){
$waitlistUser = get_user_by( 'id', $user_id);
if ( empty( $waitlistUser ) ) {
return;
} else {
$waitlistUserEmail = $waitlistUser->user_email;
$form_id = '18';
$entries = GFAPI::get_entries($form_id);
usort($entries, make_comparer('date_created'));
$emails = array_column( $entries, '3' );
$waitlistposition = array_search( $waitlistUserEmail, $emails );
if ( !in_array( $waitlistUserEmail, $emails, true )) {
return;
}
}
return $waitlistposition +1;
}
Only a few percent of users are on the waitlist.
I've managed to get the custom column created and to display the appropriate wait-list position of the user in the user admin table, but every guide I've found on making the column's content sortable either describe default WordPress sortable criteria, or by a meta query like I've done for other columns in the code above.
Any thoughts on simply sorting these columns by their value if the value does not actually exist as user meta or user data? The values are simple integers, starting from 1 and going to 100 or so.
I've tried leaving the created column alone, and although it does have the arrows indicating it is sort-able, clicking it does not change the order of the entries, and trying to force a query like the WP_Query used earlier, of course, results in a blank table once I try to sort.
Thanks for reading the long question about my simple problem! Also happy to hear if making the wait-list position into some sort of dynamic post-meta may make more sense.