Weeeeeellll... Yes that would work.

But (as a reader: ie: when initially reading this) the first thought that popped into my head was... "WAIT! They're sophisticated enough to keep a box orbiting a planet (a planet they terraform!!!) that can create new LIFE and they don't have technology enough not to lose contact with each other on landing???!!?"

So I thought and said "Well, maybe they crashed, and lost contact anyway"

Then I said, "yeah, but they created DRAGONS, *after* landing, so they could have just created a horse-like cheetah-speed mule-bird or something that could carry a message, quickly, to the other civilizations."

And before too long they'd be mingling again....

So, after a 10 minute convo with myself (I'm an excellent conversationalist, when I'm the one who's listening) I figured the only way that would work is if 1 of the people crashed and lost ... well... everything... even contact with the Melody Box. Then their civilization would devolve, while the others thrived, and they would spread/migrate and THEN they might evolve differently.

But honestly, it seems way too complicated to make it enjoyable, and I liked where you were going better without the whole "evolving vulcans" issue thrown in :/