There is no correlation to the contacts you add in the admin center Former internal Skype for business contacts were migrated some time ago but unless from this you have to manually add the contacts in teams! There are afaik currently no option to automatically add contacts for all teams users
Best Response confirmed by
nicb (Occasional Visitor)
Adam is correct. You cannot add contacts to your contact lists for Teams. You must click new chat button and start typing to get returns from your directory. However this will only return User accounts not Mail contacts. Adding any federated contacts to your contact lists are still not supported. They will be importing existing ones in the near future, but until they you must manually type in federated contacts to chat with them. You may pin them in your recents list.