In this case it's just a figure of speech. You don't actually have to trust me. You can read Dennett's book and see for yourself.
What evidence do you have of this? In fact, the majority of practicing philosophers are actually physicalists (56.5%):
It seems like it'd be the next logical step: if consciousness is simply what (sensory) computations feel like "from the inside", then it stands to reason that other computations can also "feel like" something from the inside, regardless of the substrate they run on, no?