What kind of validation is run on spec upload?

I'm getting this validation error:

The spec you uploaded has validation errors that must be addressed. Here's what we found:

Validation failed. /paths/authentication-settings/saml-metadata-upload/put has a file parameter, so it must consume multipart/form-data or application/x-www-form-urlencoded

I tried validating my spec against the json schema for swagger 2 from here : https://github.com/OAI/OpenAPI-Specification/blob/main/schemas/v2.0/schema.json and it validated successfully. So my question is what extra validation does readme.com does on swagger spec?