Yes, a bunch of different texts, gathered into ONE. So it becomes a single source.
They only count as a single source in the context of establishing the historicity of the contents. That is just how historical research works. In order to validate the historicity of a given source (in this case the bible) you heed external sources for comparison.
We are also referring specifically to the crucifixion, you can not use the OT as a source, because THE CRUCIFIXION IS NOT IN THE OT BUDDY!
Now for all of the denialism, that is simply the fact. This thread is about historicity, and you need sources external to the bible in order to establish it.
Why would I do that? Perhaps your reading comprehension is an issue - you are gojng off on some wierd and irrelevant tangent. The topic here is the crucifixion, an event for which external validation is needed.