The first sentence you have here has "nämä" in it, so they are talking about these two particular people, and it calls for "ovat", plural, "nämä - ovat". Here it is just two dogs "kaksi koiraa rakastaa", kaksi rules here: "kaksi- rakastaa". Perhaps, someone can explain better, but maybe this explanation will do for now.
I know it is used in spoken language, but “to love” is a stative verb, so it is not grammatically correct to use it in progressive tense. Stative verbs show and imply emotion already, so when you conjugate it in progressive, you are doubling the effort. DL is making an effort to use proper grammar, therefore “loving” cannot be accepted as correct.