Most of the tags coming with PivotX itself are located in modules/module_smarty.php.
I have taken a brief look and the entry implementation does not accept a sort parm.
As there are 2 implementations needed for flat file and sql the routine points to get_next_code (same folder in entries_flat.php and entries_sql.php).
As you can see there currently only date is used to decide what is the next entry.
You maybe already know this but development of PivotX has long stopped. We only do error fixing now.
You could try to fiddle around yourself with this code but as it is core code it could be replaced in future by an error fix.
Another option could be to code a weblog in the smarty theme template for the entry with exactly the same specifications, go through this entire weblog and create an array for all entries, pick out your current entry and use the previous and next occurence in the array to create prev/next links from.
Quite some code for experts...............
Quality is in the detail of things............
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