No, I don't think you get back links to all 100 hubs of yours. Typically a RSS feed directory will fetch the last 10 entries in your RSS feed. So you only get links for the last 10.
But the advantage of RSS directories is that once you submit to them once they will keep building links for you in the future. Imagine submitting to 30 RSS directories. So the next time you publish a hub 30 links from those sites will be created automatically for you.