Which is exactly Dennett's point in context: the idea that you are a brain in a vat is only conceivable if you don't think about the computing power that would be necessary for a convincing simulation.
Dreams can be quite convincing simulations that don't need that much computing power.
The worlds that people who do astral traveling perceive can be quite complex. Complex enough to convince people who engage in that practice that they really are on an astral plane. Does that mean that the people are really on an astral plane and aren't just imagining it?
The way I like to think about it is that convincingness is a 2-place function - a simulation is convincing to a particular mind/brain. If there's a reasonably well-defined interface between the mind and the simulation (e.g. the 5 senses and maybe a couple more) then it's cheating to bypass that interface and make the brain more gullible than normal, for example by introducing chemicals into the vat for that purpose.
From that perspective, dreams are not especially convincing compared to experience while awake, rather dreamers are especially convincable.
Denn...
Another month has passed and here is a new rationality quotes thread. The usual rules are: