Refunded Item(s) not listed on order timeline when refund made via REST API

[Mat192]

Hi - this is a query about using the Shopify REST API to make a refund against an existing order.

When a staff member operating *inside the Shopify admin console* makes a manual refund of items via the admin backend we see something like :

Note the 'Refunded Items' section showing the details of one item.

When we use a REST API call (https://shopify.dev/docs/api/admin-rest/2022-04/resources/refund#post-orders-order-id-refunds) to make a similar refund, the 'Refunded Items' section is totally empty, however our required refunds have been made exactly as specified in the API request

An example of the JSON we're passing to the call is (not for either of the above calls)

Shopify tech support (what a fight it is to get through to them!) do not seem to be able to explain what is going on here?

To be clear - our desired outcome is to have the 'Refunded Items' section populated, not empty.

Are we missing something critical from the REST call?

Thanks in advance.