John Mill (1645-1707, England) published the “Greek New Testament”, 1707, with indications of 30,000 variants. This was long before Joseph Smith. In that context, Smith was just stating what scholars of the day already knew.
Does one of the varients mention Angels of Light?
Does any of them mention "teaching as you have received it"?
Do some of them mention "preaching ANY other gospel" to be ACCURSED?