It's an updated model with more variables and complexities added. Same basic idea, but with more data in it to create a more robust and complete model. In the paper, they say their next step is to add hormones such as estradiol, estrogen, testosterone, LH, FSH, etc. to improve it even more and model more aspects of CFS dysfunction.
But the importance of this paper is that they finally tested it "officially" (published a paper about it) and proved it was predictive for both at rest (pre-exercise) and post-exercise. It's also new that it indicated why Ampligen and Rapamycin only partially works.