That’s an interpretation of Gandalf I can’t say I’ve ever heard before.
When Balin is explaining to Bilbo why Thorin hates Orcs the way he does; he tells him that Azog the Defiler had sworn to "end the line of Durin".
Now, lets see: Thorin is wandering from place to place, looking for his long-lost father, his whereabouts not easily known. Gandalf plucks him from obscurity, puts him out in the open with 13 of his kin, including his two heirs, thus, in essence, putting a bullseye on his back.
He takes him to a back entrance to the kingdom of his sworn enemy; and, then disappears as he is wont to do.
Thorin, his heirs and kin and now on their own on a "quest" that Gandalf promised he would help them with; but, as is his wont, he disappears.
At the end, Thorin has completely lost his mind, he and the only other heirs to the Throne of Durin (Kili and Fili) die with him and the line of Durin is ended. Great work, Gandalf. It has made me wonder if he was working for Azog all along. (Okay, I'm kidding about the last part; but, Azog has gotten his wish.)