Ok so it turns out I was dumb and did actually provide an empty name in the payload, the name was taken from the e-mail address instead. This is fixed now, so the Admin-Users view is now working as expected.
However, the name does still not appear in the the user’s profile settings page when using SSO. So there’s a minor bug here. Maybe this is related to the sso_overrides_name setting (which is true on my install)?