I don't think that is true at all, and indeed very few actual historians (rather than theologians or bible studies people) actually engage with the historicity of Jesus for the simple reason that you can't actually detach the history from the theology as the only evidence we have is from documents which are primarily theological rather than historical.
I'm not sure this account of where genuine historic study has taken place is familiar. Engaging with the historicity of Jesus? What do you mean by that...and why aren't you giving me the alternative of Jesus as myth? So far what your a dancing around is coming out and declaring that mainstream historians think that Jesus is more likely a myth. I have to say that would make mainstream actual historians of people like Carrier. I'm not sure they fit that description but wouldn't say that because they are considered fringe theorists they wouldn't be capable of performing genuine history.
So I don't think that historians in any shape or form agree on the secular parts of Jesus' life and ministry.
or ecclesiastical history of any sort?
Or if they do it is to say that the evidence we have is very unreliable from a historical perspective
example?
and therefore we agree that we cannot say very much at all with confidence about Jesus' life at all beyond the likelihood that there probably was a historical person called Jesus
Common name, what is it then that prevents these people saying that Jesus is myth?.
Indeed there is a train of thought that the theological Jesus was based on not one but several people and older traditions - a kind of cut and shut character that ticked all the right theological boxes.
Yes it's called Jesus as myth.
This all seems to lead to the same inversion of mainstream with fringe that you have already demonstrated.
Also the thesis you seem to present here is you dismissing the early Christians as people who obviously are a special case of making stuff up. And that theologians and biblical studies are not at all historically minded or indeed capable of Historical study.
Cut and shut might be a good description of the Jesus as myth formulations of which myths Jesus is made up of. A methodology, I move, that has put them on the fringe.