Censys expands queries to provide additional functionality. For example, the query a:zmap.io
executes a DNS lookup and expands to ip:141.212.120.90.
Your query was changed from:
(parsed.signature.signature_algorithm.name:SHA1-RSA) AND tags.raw: "unexpired"
to
(parsed.signature.signature_algorithm.name:SHA1-RSA) AND tags.raw: "unexpired"
If this isn't what you intended, you can run your raw query without expansion.