How are we supposed to use Dogmeat?

His perk is "X3 Objective Completion."

Okaaaay.. what does that mean? How do we use him? When we give him to someone, what exactly happens?

E.g. Get 9 dwellers pregnant... If dogmeat is in the room you need only 3 (you also get only 3 babies)

I wish I had a Dogmeat, I have a x2 objective pet and feel it is the best pet I have. Reducing objectives by 1/2 saves a lot of time completing objectives.

I've more or less abandoned 2 vaults because of dogmeat. Most valuable pet by far in my opinion... I'd love to have 2-3 of them.