I don’t know what you tested, but the latest OracleDialect in Hibernate ORM 6.2.0.Final does not map NUMBER(1,0) to Boolean anymore. The mapping to FLOAT is a special case that only happens if JDBC reports a scale of -127, which seems to be a special value that indicates float semantics.
The JPA specification doesn’t say anything about how we should interpret native query results when no result set mapping is given. Usually, we try to follow map native query results similar to how we would generate a schema though. Since we generate NUMBER(10,0) for persistent attributes of type Integer, we try to map that back to Integer then also.