This religious concept was common in the first two certuries or so, AD. I find it rather surprising that these academics find this "unique".
One can visit the ancient tunnels underlying Rome today, and see burial markers and carvings containing both Christian and pagan references (on the same monument). These are particularly frequent in the tunnels that lie directly under the Vatican (which was built on the site of both a pagan temple and a first century cemetery).
Biblical scholars theorize that since Christianity was the new religion on the block during this period, many believers were "hedging their bets" so to speak........particualrly during burials.
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