The answer linked in that other post shows that you need to merge two arrays, one searching the titles and the other searching the meta_query.
http://wordpress.stackexchange.com/questions/78649/using-meta-query-meta-query-with-a-search-query-s
I’m just wondering if this is beyond the scope of adjusting the search that happens for relationship item types in ACF. It seems like I can only manipulate the $args, and not the query itself, in order to merge two queries.