There's no point in pulling a blood relative into DNA analysis if there's no DNA from the body to compare it too.
OTOH, as I've written before, San Diego County could decide to spring for the more expensive (and time consuming) attempt to extract whatever (perhaps scant) DNA might be in tiny amounts of collagen still within the skeleton (for example, in the spine). There are really expensive techniques (and probably only a handful of professors who can do it) that attempt to reconstruct DNA from super-microscopic evidence within the marrow chambers. Mitochondrial DNA is the most likely to be found - and that would establish JRF's identity only if they then got DNA from his mother or a sibling from the same mother - and since there are so many other clues that it's JRF, I suppose that could be considered somehow more conclusive than merely finding his clothing, truck and possible some ID nearby.
I can't find the source that says they found ID, but I believe I read it here and we've discussed. IF no idea, the truck being up there and Jin Fang's identity being established should be enough - I don't see why San Diego should have to spend six months and tons of money for a process that is not certain to provide any more data.
This article from 2015 is about "ancient" bones but is relevant to contemporary bones with severe weathering:
Poor DNA preservation is the most limiting factor in ancient genomic research. In the majority of ancient bones and teeth, endogenous DNA molecules represent a minor fraction of the whole DNA extract, rendering shot-gun sequencing inefficient for obtaining genomic data. Based on ancient human...
www.nature.com
The article describes the process (which is not the process used by regular forensic labs to obtain STR data). If there's such a lab in San Diego, it would likely be at UC San Diego, and if so, then they could ask the professor who runs the lab to use the enzymatic sequencing process (or its newest iteration) on the bones. Maybe that's what they're doing. But they cannot expect such a lab to simply drop what they're doing for their own research and do this as an emergency - if the person running the lab has time to do it (and I would expect they have to pay for the time they use), then it would get done sooner.
That may be why the final, positive identification of JRF has not been completed. This type of DNA is kind of like a mirror of the real thing, found in two places in a skeleton:
"hydroxy-apatite aggregates and within the organic collagen fibrils"
(from the above article. The hydroxy thingies are found in the bones). It's been pretty successful. Article also mentions teeth roots, which are apparently not available in this case. To do this research on JRF's bones, some bone would have to be destroyed - and for that, I'd imagine, some kind of permission would be needed from the family of the suspected person. I don't know the legalities of this, but if it were to turn out to be someone else, then it would be quite awkward for San Diego County to have destroyed parts of human remains without permission. Hence, the tentative identification (which is almost surely accurate). This expensive DNA test would be confirmatory of the other evidence, if it worked. Which I would think it would.
The toothbrush method can't work unless they have DNA that's from the actual body to match it to.
IMO.