Difference between adding a owner trough O365 groups or SharePoint online

Hi All,

I have a question regarding the difference between adding a user as owner trough O365 groups (admin portal) or adding it via the SharePoint online website.

Example:
I have a SPO Teamsite: Team1
When I go to portal.office.com and add User1 as Owner to the O365 Group matching the SPO site 'Team1'. I get access to the SPO site. But don't get the 'welcome mail'. Also the site is not visible in the HubSite I created, neither can I search contents trough SPO search.

When I add User1 via the SPO TeamSite by pressing Members and 'Add Members', i do get the welcome email, and it is visible in the HubSite and searchable. 

Does anyone know if this is expected behavior?

Thanks.