Censys expands queries to provide additional functionality. For example, the query a:zmap.io
executes a DNS lookup and expands to ip:220.127.116.11.
Your query was changed from:
parsed.names: (dns_names or us133-pl.valueserver.net)
parsed.names: (dns_names OR us133-pl.valueserver.net)
If this isn't what you intended, you can run your raw query without expansion.