Did you notice that the link in the comment you were replying to, has a photo of that “Appeal to Heaven” flag from a Black Lives Matter protest in 2020? And it seems clear it was being flown by BLM supporters, not anti-BLM counterprotestors.

You want to claim that other meanings are purely historical and in contemporary usage it exclusively means “white Christian nationalist”. If the only other examples of its usage people could point to were from decades ago, your argument might have some force. But, given we have photographic evidence of people with a diametrically opposite ideology using it less than 5 years ago, your argument is not very convincing.