Looks like that part of the system was refactored back in v13. I think searching “actions” may have been a side-effect of how the token search works, rather than intended functionality. The downside was that any class or user with substrings in their name that overlapped with the words “action”, “class”, “staff” were nearly un-searchable because of the number of other strings that matched it. When that piece of the code was refactored, it was replaced with an AJAX-based search, which excludes the prefixes on the token text. I’m tempted to say because of the downsides of the old behaviour we’re not likely to change it for the core, but you could always edit the index_fastFinder_ajax.php script if it’s something you wish to keep.