I know, what does that mean, never assume? It means just because someone is in the right place at the right time doesn't make them the right person. I know that sounds crazy. If it looks like a duck and it quacks like a duck, isn't it a duck? The best answer I can give is it might be a duck but then again it might not.
Example: For years I thought I was descended from Digory Sargent. His son Daniel was kidnapped and carried to Canada in 1703/04. He was taken to Montreal and I did often wonder how we got the long way up the river to Cap St Ignace. Well it seems, he didn't. DNA has proven that he isn't our ancestor. It needs a few more tests to really be proven but it seems obvious now that all the things that didn't quite fit, actually didn't fit at all. Someone assumed wrong. So, yes it wasn't actually a duck.
DNA has made it easier to verify assumptions but not fool proof. So, when you find something that you can't prove, assume it might be correct and save all the information but don't stop looking for the truth. Unfortunately, our ancestors weren't interested in making sure they made their information clear and easy to follow and often our trail is very twisted as wee strive to arrive at the truth.