$ref ignores any sibling associated with it about openapi-specification HOT 1 CLOSED

What you are seeing is a limitation in OAS 3.0 and earlier.

In OAS 3.1, $ref in Schema Objects can have adjacent properties in accordance with the rules of draft 2020-12. For validation keywords, this is just the same as using an allOf. For annotation keywords like description, deprecated, readOnly, etc., it is up to the application (e.g. Swagger) to decide how to handle the adjacent keywords. They are not necessarily overwrites as not all annotations have the same semantics.

Also in OAS 3.1, $ref in the Reference Object allows exactly two adjacent keywords: summary and description. These are overwrites (unlike in the Schema Object).

Since OAS 3.1 has already addressed this issue, I'm going to close it. For Schema Objects, if you want different behavior from what OAS 3.1 does, you need to file that with JSON Schema as 3.1 just uses standard JSON Schema (unlike 3.0). For Reference Objects, if you want additional adjacent keyword support, please file a specific issue for that.

from openapi-specification.