Though I've already answered you, I'm perfectly willing, as devil's advocate, to go with your selection "a." Since, as the paper I cited states, there are tens of thousands of unambiguously matching, indel free, no manipulation necessary, ERVs.
Great then at least we agree on that....the reality is what is...(including real ERVs)
Therefore when we begin counting base pairs and we come upon a place where the two sequences do not match, then it is equally plausible that an excuse or explanation is not required. We simply can let the differences be seen as just what they are...differences in each respective organism's genome, thereby not having any need to label them them additions or subtractions to support some presupposed notion or paradigm.
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