Consider this definition:

components:
  schemas:
    Foo:
      type: object
      properties:
        inline_enum:
          type: string
          enum: [one, two, three]
        referenced_enum:
            $ref: '#/components/schemas/ReferencedEnum'
    ReferencedEnum:
      type: string
      enum: [one, two, three]

If you generate PHP from this defintion using a modelNameSuffix=DTO option on the generator, the values of inline_enum will now change from being e.g. INLINE_ENUM_ONE to INLINE_ENUM_DTO_ONE, which doesn't make sense.

Values of ReferencedEnum are untouched, still ReferencedEnum::ONE (though they are unusable regardless for another reason).