Daddy,
Maybe it is just semantics, but I would say the term "invited" walk-on or "recruited" walk-on would differentiate a player who was recruited, from a walk-on who just showed up and tried out.
I never heard the term "preferred walk-on" but if that is the term that most college soccer programs are using nowadays, then I learned something new this week.
I'm not pooh-poohing walk-ons. I played D3 college soccer, so technically, we were all "recruited walk-ons" and regular walk-ons.