Amusingly, Grant wrote a book on the historical Jesus in which his conclusion is that Jesus was an apocalyptic preacher expecting the imminent end of the world. Which didn't arrive. So when he says Jesus must have existed, his Jesus is not that of the WBTS and almost every premise they take for granted to make a conclusion is flawed by citing him as support.
When I asked about some of the issues I saw around gospels and accuracy, I got the 'holy spirit did it' answer and questions about the strength of my faith. Which is the way it always went with awkward questions. The bible is always 100% accurate and correct. Apart from the bits where the writer needs a bit of help from Brooklyn in conveying what he really meant to say...