No exact answers, but...
Android is modified by individual vendors, so the contact behaviour may vary between manufacturers, and possibly between models as well. Many manufacturers try to differentiate some things in their phones, and basic functionality is sometimes targeted for further integration, e.g. one vendor may decide to scan your Facebook, Twitter, and Linked-In accounts, etc. So, check the documentation for your specific device for precise answers if you end up finding that something "isn't right".