@nickdanielle
Try the XPATH or JCR-SQL2 equivalent of the above query which has support for wildcard character in jcr:contains
(You can arrive at the same using Explain Query: Tools -> Operations -> Diagnosis -> Query Performance -> Explain Query -> Key in your Query builder predicates -> You can see the XPATH and JCR-SQL2 equivalent and index used)
There is no explicit mention about wildcard support in fulltext Query Builder predicate.