More likely, it's that there's a correlation between low intelligence and religiosity (https://en.wikipedia.org/wiki/Religiosity_and_intelligence). And, of course ,there's a correlation with bad spelling and low intelligence.

So a religious person is more likely to be okay with spelling mistakes because they themselves are likely to not be good spellers, because they are likely to be less intelligent. It has nothing to do with religious people being okay with small mistakes.