The colloquial use of the word "ain't" here very specifically pegs James Bruce, the author, as writing his argument for an audience of Christians in the Southern part of the United States. It's even more stark as most of his review is of a broadly scholarly nature where the word "ain't" or others of its register would never be used.

How does the shift in translation really negate room for Jesus? If it was a truism that it stood for Jesus, then couldn't one just as simply re-translate the New Testament to make sure that the space for him is still there? Small shifts in meaning and translation shouldn't undermine the support for Jesus so easily as Bruce suggests, otherwise there are terrible problems with these underpinnings of Christianity.

If one follows Bruce's general logic, then there's a hell of a religion based on Nostradamus' work we're all going out of our way to ignore.

What would historical linguistics have to say about this translation?

https://www.investopedia.com/terms/t/tanstaafl.asp