Walk-ons vary by school. The #1 on my kid's team was a walk on and he is headed to an SEC team next year. One of our top bullpen arms is a walk on and pretty sure our best hitter who is also headed to an SEC team was a walk on initially. The coaches don't seem to give a damn about anything except who will help the team win.
Ask any parent who has had a kid play at Arkansas about walk-ons vs scholarship players. If you are on a big piece you better contribute big time. Arkansas and Oregon State have both used recruited walk ons extensively.