Lipkin is interested in the hit-and-run theory. I assume this is because he's a pathogen hunter and he's been unable to detect any convincing patterns of pathogens, so far, that he would usually expect to see in an infectious disease.
All it means is that there is a microbial trigger for the illness. i.e. Perhaps a pathogen (or a variety of pathogens) is involved in triggering the illness, but it becomes undetectable after initial infection, but leaves a lasting biological effect?
I suppose this could also be the case for many other diseases with unknown cause (e.g. Parkinson's, MS, Alzheimer's, schizophrenia.) We simply don't know what mechanism triggers or drives the illness, so it seems sensible to entertain various concepts.
I'm convinced that Lipkin is open minded and wishes to carry out a comprehensive investigation into ME, and will follow any research leads. He's not dogmatic, so he's not just pursuing one specific theory, as far as I understand.
Part of the reason that he's looking at the gut microbiome is because he's not found any pathogens in the blood plasma or cerebro spinal fluid. (He's detected a couple of viruses but there was no difference between patients and controls.)
He's also looking for pathogens in blood cells.
Basically, he's covering it from all angles and the hit-and-run theory is one of those angles.
He's looking for viruses, bacteria and fungi in the gut microbiome. Something unexpected might turn up. And he's also looking at immune markers in the same patients (e.g. cytokines) to see if any changes in the gut correspond to changes in cytokine levels. He's done similar research for autism, and has uncovered some leads.
And he plans to do a proteome study of CFS patients, which may prove to be very interesting. (I think Dr Hornig may have started this already). And there's more that he's either planning, or has already started, but I'm hopeless at remembering it all. And I get the feeling that he's only told us a fraction of what he's up to.