You’re absolutely right about subvocalization being a relic of voiced reading (reading aloud). I can overcome it if I really work for speed, but it makes a labor of a love. So unless I’m just trying to blaze through something ridiculous like “Ulysses,” I subvocalize and devil take it!
I wouldn’t try to speed read Ulysses! Tough enough to read it nice and slow. Literature, per se doesn’t benefit from speed reading unless you are going to take a test on it. I found the high speed stuff very useful for reading for getting information. Also made reading students’ papers a bit easier—a whole page in a couple of seconds.