First, you're probably confusing this report with another one saying the venusian-style runaway greenhouse will take longer than expected.

The general idea that we had .5 to 1G years before a runaway greenhouse would cook Earth has little relationship to the strong consensus on anthropogenic global warming. All the new study says (if correct) is that it will take longer.

I'd say the relationship of this question to AGW is in the maturity of the science. The fate of the Earth over billions of years is something we understand right now to the same extent that evolution was understood in the 1870s - we know the concept, but a lot is poorly understood. Our understanding of AGW today is similar to late 20th century understanding of evolution, where we've spent several decades of sophisticated scientific analysis, field experimentation, and billions of dollars to figure things out.