This is a much, much, much less complex and rich semantic relationship with the outside world than the brain had before. So you would expect it to drastically change the brain's state and hence its consciousness. I don't think you have fully considered the implications: the brain would have no sight, no hearing, no smell, no taste, no touch, no kinesthetic sense of its body, no sense of hunger, thirst, no sense of heartbeat, breathing, etc., etc, etc., I could go on and on. And that's just the sensory side; the motor side is a whole other can of worms that you haven't even mentioned.

> Are they suddenly not conscious, because they no longer have some transcendent connection with reality?

I don't think anyone can make authoritative statements about what this kind of scenario would be like. But to answer the question exactly as you ask it, the answer is "mu" because the claim was not that consciousness requires any kind of "transcendent connection with reality", it was the much more mundane claim that the kind of knowledge we humans have is based on an extremely complex and rich physical connection with the rest of the world.