When returning integer, bigint, smallint, boolean and float values, the oid on the wire is 25, meaning data of type text. In contrast, date fields and bytea fields for example are sent with the correct oid. I see also that there is support for determining the PostgreSQL oid corresponding to an SQL type in map_sqlite_to_pg_type.
It would be useful if the on-the-wire oid was correct, because some PostgreSQL client libraries use this information to parse the data into the corresponding type in the host programming language.