Unfortunately, this is not possible, as the endpoint {{url}}/api/v1/apps/{{appId}}/users/{{userId}} is used to return the user’s application assignment profile.
The solution is to use this API to change the user’s password and then do a request to /api/v1/users/{{userId} to retrieve the passwordChanged field.
The API described here refers to Secure Web Authentication (SWA) applications in which you save the credentials in Okta and then, after clicking the chiclet on the end-user dashboard, the Okta browser plugin injects the application credentials automatically in the app’s log in page.