No real problem with this, many groups are put together/manufactured by agents, execs etc. It's more difficult for groups with complementary voices and abilities, look, influence, style and so on to form organically. As we've seen, 4 of Diamonds can sing and are worthy of a place in the live shows, certainly more worthy than The Brooks and Bratavio were.
The only implication for their being formed (for me anyway) is that this whole "We love the 60s" shtick now appears inauthentic, as it was likely cooked up by the producers. And what do you know, just as they're about to return, the theme chosen is Motown.