See notes for character 11 here:
https://www.loc.gov/marc/authority/ad008.html

n - Not applicable
1XX heading is not a name, name/title, or uniform title formulated according to descriptive cataloging rules and is not appropriate for use as a main or added entry in bibliographic records. 

We need a negative search, or another way to exclude this from matching, they are valid for 1XX, but not 6XX