False positive: Adding a subschema to a oneOf is not breaking

[adamchalmers]

I have two API schema:
api.json
old_api.json

The only difference between them is adding a new subschema of a oneOf:

As far as I understand, this should be considered a purely additive change, not breaking. But openapi-changes considers this a huge change with many breaks:

This is using openapi-changes version: 0.0.88 | compiled: Tue, 23 Sep 2025 19:19:14 UTC.

[adamchalmers]

I think this was because it's under components.schemas which could be either a request or response body. But this particular schema is only ever referenced as a request body. If a oneOf can only ever be a request body, then surely adding a new variant is only an additive change?