"+ Install new module" button doesn't appear after installing Update manager module

"+ Install new module" button doesn't appear after enabling Update manager instead it appears after clearing all cache.

Steps to reproduce :
1. Install fresh Drupal instance , go to "Extend" tab that will route to Modules page .
2. Enable Update Manager module.
3. See after enabling , we can't see an Install new module button that would help to install new modules.
4. Issue : Install new module button appears only after clearing cache.

Accepted Behaviour:
1 . As a Drupal user , I need to install new modules using Update manager
2. After enabling Update Manager module , I should see "Install new module" button on Extend configuration page . It appears only after clearing cache so I think this should not be an accepted behaviour.