Sorry for the many ‘groups’ in the title… I tried to be precise 
In the documentation it says a group owner (with the needed invitation rights) can Invite users to a group via the button on top of the list of group members.
A popup appears and this is my observation: If the group owner is just using the ‘Create link’ button on the first popup without clicking the button to configure options, the invite will not lead to the specific group. If they use the ‘Create link’ button on the second popup the invite parameters are correct and it leads to the group. It is the same for admins as for regular group owners.
On our disourse instance the users should not roam freely without a specific group. Each group owner independently decides who joins the platform and their group. But if users get invited onto the platform without the proper invite to group route they end up in a sort of limbus where nothing happens. So if it were to us, the group owner should solely be allowed to invite users to their specific group. But it could be that just the documentation is incomplete, if my observation matches the intended behavior 
Hint: Activating`enable_invite_modal_with_roles` lets one work around this issue, as the new popup always invites to the specific group, whether you configure the link options or not.
(Tested in 2026.7.2)