That's a difficult question, since a (without) gnostic (knowlege) means "don't know". Intuitively I've have to trace it to the praxis of the individual who embraces that. Do they live as though God exists, apart from the obvious use of the laws of logic and reliance on an orderly universe? The only acknowledged agnostic I knew had a very weak faith, and occasionally prayed the Lord's prayer having been raised Lutheran...
If they are teaching positive doctrine (part of a system of thought), rather than naysaying both theistic (God-centered) and humanistic (man-centered) religion, it would seem so. But to do that would undermine their whole premise.