I think what's happening here is that the theist's preexisting belief about a creator god is causing them to privilege the hypothesis of divine RNA-creation.

The trouble is, you seem to be privileging it too. The way you've set up the scenario makes it seem like there are two hypotheses: (1) goddidit, (2) some unknown natural process.

But (2) is actually a set of zillions of potential processes, many of which have a far better prior than Yahweh and the Thousand Claims of Scripture, even if we can't actually choose one for sure right now. Taken together, all their probability mass dwarfs that of the goddidit hypothesis.

You don't have to know all the answers to say "you're (almost certainly) wrong."