Cannot add certain apps in non public Teams created by Graph API

We found a very strange issue at several tenants, regarding Teams creation via the Graph API: when a new Team is create with the Graph API, which has Visibility != "Public", in the created Team you cannot add the Flow app (and possibly other apps will have the same issue...).

When a new Team is set to Public, the issue does not occur.

When creating Teams via the default user interface, the issue does not occur, neither for Public nor Private Teams.

What I've tried so far (and still gives the issue):

• Creating a Group OOTB and extending it with a Team
• Using PUT /beta/groups/.../team to extend with a Team
• Using POST /beta/teams to create the Team directly, instead of extending a group
• Cloning an OOTB Team using the Graph API
• ...

It seems that anything that's being done with Graph API which creates / changes to a non public Team has the issue.

Also: https://github.com/microsoftgraph/microsoft-graph-docs/issues/7567