Regardless of how WDFW is rumored to feel about it, I have a hard time believing that tossing a line without a hook could stand up in court as "fishing".
Just as an example, here's a couple related
state law definitions about fishing (and keep in mind I'm no lawyer)
I don't think that a rod with no hook fits either of those. I suppose someone MIGHT be able to claim that you were intending to "harass" fish in closed water? But I feel like there's a big "intent" aspect there that any competent lawyer would grab hold of. Now, how interested are you in dealing with the hassle that would come with an overzealous LEO trying to interpret the law to say that you were in the wrong?
All that said, I think a call/email to the WDFW for clarification is probably a good next step. I'm sure lots of us here would be interested in the answer.