Customer Auth has no refresh_token

Authentication & Access
1

I am trying to set up Customer Accounts API authentication OIDC for my App.
The resources that I use:

Getting started with the Customer Account API (Is using the Headless Channel)
Authenticate customers with the Customer Account API (Tells me how to do it for an App)

If I authenticate using the headless channel I can receive an access token and a refresh token.
If I authenticate using my app I also receive the access token but no refresh token. (I do receive an expires_in value)

I could not find any mention, that there should be a difference between how I authenticate. There is also no mention that the refresh token is optional.

The only difference between my two auth flows is the client id.

2

I am also facing same issue while testing the implemented oauth authorization with PKCE for customer account mcp server integration on my localhost env. I am getting access token but refresh token field is not present in the token url response.

Please tell me whether it is expected behavior from Shopify, or I am doing something wrong related to scope settings?