They've definitely retconned their own story. I am 99.98% sure that Rasputin was the one that stopped the traveller from leaving. Correct me if I'm wrong, but I haven't read anything about "the traveler decided to expand its light to drive back the darkness and that's why it's stuck in our solar system." The traveler only sent out ghosts to "help us" after Rasputin crippled it so that the Traveler only had two options, send out ghosts to develop a defensive army, or die when the darkness arrived.