Censys expands queries to provide additional functionality. For example, the query a:zmap.io
executes a DNS lookup and expands to ip:184.108.40.206.
Your query was changed from:
parsed.names: (dns_names or *.wpengine.com)
parsed.names: (dns_names OR *.wpengine.com)
If this isn't what you intended, you can run your raw query without expansion.