Exam AD0-E718 topic 1 question 4 discussion

An external system integrates functionality of a product catalog search using Adobe Commerce GraphQL API. The Architect creates a new attribute my_attribute in the admin panel with frontend type select.
Later, the Architect sees that ProductInterface already has the field my_attribute, but returns an Int value. The Architect wants this field to be a new type that contains both option id and label.
To meet this requirement, an Adobe Commerce Architect creates a new module and file etc/schema.graphqls that declares as follows:

After calling command setup:upgrade, the introspection of ProductInterface field my_attribute remains Int.
What prevented the value type of field my_attribute from changing?