It actually is possible to get the body of a news story with JET, but it is definitely not very efficient. The news story may be split into many small parts, and it may take many separate calls to get the full story. This needs to be done sequentially - you need to get the 1st in order to know what the 2nd part is, and need the nth to know what the n+1st part is, or if there actually is a n+1st part.
From my experimentation, you end up watching the story arrive, 1-2 sentences at a time. I have seen a story of just moderate length that was split into 45 parts.
[It may be that this method, aside from slow, tends to degrade performance. I am certainly not advocating for the use of this technique.]
However, there are (in my opinion) legitimate reasons to want to retrieve story text in JET. Given the performance of the news object, clearly a more efficient method is possible.