"It would be silly to doubt them"
I agree to an extent, is there information true? Yes, but despite them having inside information they are still not always right (EX: PTG said that the location of Buried was at the "Horn of Africa" which was incorrect). They still get stuff wrong so I don't think Treyarch tells them everything.
Is it still a possibility they could be wrong? Yes.
Can you deny the evidence of the next map being set in WW1 and France? With hints coming out of the next DLC and the date "1917" No not really. France? We'll just have to wait and see.