I think it's more that. Make people sick of the issue before the election. Then by the time we get to the general and Trump goes, "Hey it's Pocahontas," the result is a collective eye roll, but not some damning argument.
And it shouldn't be a damning argument. The truth is that Warren had no reason to disbelieve her mother's stories that she was part Native American, and the more important truth is that Warren never benefited from any claims about her ancestry.
She is a strong candidate with and inspiring life story. She's from very humble Oklahoma roots, she's overcome a lot of adversity.
Oh, and by the way, our current POTUS is a white collar criminal whose wealth came from tax fraud schemes.