When I first heard of this line of evidence (Plagiarized Errors and Molecular Genetics: Another Argument in the Evolution-Creation Controversy, Creation/Evolution Journal (CEJ), Winter 1986-1987, pp 34-46), its significance was explained through the analogy of fictitious items in catalogues, directories, and other reference works. If somebody else later publishes a work on the same subject matter, how could you tell whether they had done their own research as you had done or they had simply plagiarized your own work? After all, two different people researching the very same information (eg, a phone directory or map) should be expected to come up with the same directory.
Well, if you added false and hence useless items and those same false (ie, fictitious) items also show up in the second reference work that you suspect of being a plagiarism, then that's your proof in your copyright infringement lawsuit. If those fictitious items are missing, then it's most likely not a plagiarism.
Do you remember Sidney Powell filing an election fraud lawsuit citing reports of election fraud in Edison County, Michigan? The slight problem with that is that there is no such county in Michigan, nor anywhere in the USA for that matter. Since you can look up counties on Wikipedia, I tried to look it up and at that time (early Dec 2020) it redirected me to the page, Fictitious entry:
quote:Fictitious or fake entries are deliberately incorrect entries in reference works such as dictionaries, encyclopedias, maps, and directories. There are more specific terms for particular kinds of fictitious entry, such as Mountweazel, trap street, paper town, phantom settlement, and nihilartikel.
Fictitious entries are included either as a humorous hoax or as a copyright trap to reveal subsequent plagiarism or copyright infringement.
So the analogy is that you should be unable to tell whether the genes for a useful feature in two different species being the same or nearly the same is because of common ancestry or had simply been created the same way since they served the same function (ie, why expect God to not be able to simply reuse something that works?). But having embedded non-functional genetic code such as ERVs also show up in species that seem to be related, then the only explanation would be common ancestry.