I don't think the Coyotes can legally claim Kerensky bloodrights, under Clan law. But a lot of funny buisness has gone on during the Wars of Reaving. I wouldn't be just terribly surprised if some existing warriors of the Kufahl bloodhouse petitioned to be allowed to claim the Kerensky name as "first generation descendants of Andery Kerensky" or something like that. I don't think the Coyotes still have a copy, nor do I think hey can produce more such sibkos, but it wouldn't surprise me if political maneuvering led to a restart of the Kerensky bloodhouse through such warriors, even if it violates Clan Law. After all, in the Clans might makes right. A Trial of Refusal makes it a valid interpretation of Clan Law.
The problem with your argument is the manner in which clan law decides matters; No other clan could use matrilineal Kerensky DNA because the Wolves defended their claim to those legacies. Once the Wolves are abjured, as far as the homeworld clans are concerned, they have no standing to conduct a Trial of Refusal against another clan's use/claim on those legacies OR defend a Trial of Possession for those genes.
In theory, IF such DNA were available, all the homeworld "clans in good standing" could compete amongst themselves to have possession/control of said DNA.
Say the Coyotes announce that they will use Andery's DNA from storage to re-establish the bloodhouse in the homeworlds; the other clans are well within their rights to request Trials of Possession for access to that DNA, which the Coyotes would have to defend.
Now suppose that the Adders have in their possession the DNA of a matrilinearly-descended warrior of Andery’s bloodhouse they captured as abthaka; they have, in theory, the control of the physical DNA of Andery’s line. Since the Coyotes have “priority control” (basically, they have the first generation genes; much “purer” than those of the Adder’s warrior) of the genes, they can challenge for a ToP or ToR to either prevent the Adders from using the genes at all, force them to use them only patrilinearly or gain a copy of the warrior’s DNA.
Any clan that has a captured warrior of a bloodhouse from one of the abjured clans has essentially free reign and control of that legacy, possibly turning a once-exclusive bloodname into a shared bloodname.
That being said, assuming that the homeworld clans do have access to matrilinear Kerensky DNA, the question would be if they would want to use it, given its “inner sphere taint”.