But if you don't happen to believe in God then swearing on a book of (from the oath takers perspective) fairy tails is equivalently silly / virtue signaling. I

But if you don't happen to believe in God then swearing on a book of (from the oath takers perspective) fairy tails is equivalently silly / virtue signaling. I think it's better if someone calls out that they don't believe in the thing they are swearing on and substitutes it with something they do believe in? otherwise one is making a promise on top of a lie that they also believe in the contents of that book, so the whole stack is forfeit. Or am I missing something?