Yeah the feeder road is the entire parallel road not just the on ramp. Between feeders and regular freeway exits every mile or two it really prevents some of the incredibly dangerous driving I've seen in other parts of the country where people dive for an exit because the next one is 5+ miles away. Because we typically have overpasses for intersections under the freeway it's no big deal if you miss an exit. Just take the next one 1/2 mile or a mile away and make a uturn underneath the freeway. If you aren't going far you can just take the feeder down to your missed exit.
From Houston myself—I’ve mostly seen feeder roads refer to the roads with ramps alongside freeways, not the ramps themselves. Since moving, I’ve seen them called frontage roads elsewhere.