I was wondering: could you find out when the charter boat slammer opened for business? Write them on FB? That might answer or not answer some questions.
Other thoughts: the nature of tourism in Washington State after living here for 20 years...
1) Nearly everybody who lives at or very near the Washington coast all year would love to or will definitely go to, every year, especially in Summer to: either (a) Eastern or Central Washington in the Summer (primarily Wenatchee which is east of Ellensburg) or (b) down to the Oregon Coast, which is far superior in almost every way from dramatic rock formations to shopping to food. (2) Nearly everybody who lives in Central or Eastern WA as well as Seattle/Puget Sound can't wait to go for a fun vacay at one of these three, if they are traveling in state: 1) Ocean Shores, 2) Long Beach, or 3) Westport. They are the most common destinations other than just going to Seattle itself if you don't already live there. Wesport faces Ocean Shores from across the "bay"--it takes a while to travel by road between the two. Both are basically sand spit type areas that jut out on either side of the bay. You can sometimes see the lights of Westport from Ocean Shores and vice versa at night if it's very clear out...which is very, very rare. In addition: most people who don't live on the actual coast towns of Ocean Shores and Westport go to those towns for their vacations. It's a day trip and rather boring coastline. If you go further North up the coast highway you can reach after a long drive the Olympic National Park beaches, which are considerably better, but if you don't camp there is hardly anywhere to stay. Most people living in the inland towns only go to the beaches of O Shores and Westport for things like 4th of July fireworks (Fire on the Water) in Ocean City, or for clamming during different parts of the year.
If my experience as a lifelong tourist in the Pacific NW explains anything to outsiders: hitting a coast town is a blast if you can afford, once in a blue moon, to go on a whale watching, educational voyage for kids, or fishing charter boat--it appears that the boat slammer place is one of them. One should always try to do it at least once unless you have horrible sea-sickness. So again, not uncommon for a Washingtonian who does or did indeed live in Ellensburg area to go to one of the three major coast towns in the state and go charter fishing or touring etc. Westport may be the best for that, in my opinion, because they are or were the place where the real fishing and crabbing setup is, whereas Ocean Shores doesn't....neither seems to have any real hope of catching views of whales...that's more of an Oregon coast thing to do.
The highways going to Ellensburg or Yakima, etc, on the beginning or end of a weekend are just as bad during the peak times of the summer on the Washington Coastal highways--especially on the three day weekends or Harley Weekend in Ocean Shores, etc. So, though they described the highways into Ellensburg being so overloaded by Western Washingtonians, the same is true along the coast of course. After hunting season is over, though, mostly people during the fall or winter will head to Leavenworth if they want to vacation over on the central/eastern side of WA state. Leavenworth is the thing families in places like Grays Harbor county will save and pool money for ALL YEAR so they can hopefully go there at Christmastime. It's outrageously expensive but lovely at Christmas: a faux Bavarian village that puts on plays and musicals all year but Christmas-themed plays and musicals indoors in the Winter, a Nutcracker museum, lots of German food (big roasted hocks of ham, etc), a gentle rope pull to get you back up a snowy hill so you can keep sledding, areas out in the idyllic country around the area with sleigh rides, the entire town lit up at night for a couple of months after Oktoberfest. It's a lovely thing. Terribly hot in the summer, but still it is a sign that people on the WA coast can't WAIT to get out of Dodge and go East to the recreation areas and tourism there if they can't find time or money to go elsewhere. We are all starved for Vitamin D and need sun so badly that it's like a drug...and though I hate the heat, a ton of people can't get enough of places like Ellensburg,,.until lately when it's been death to be outside there over and over again. People there: can't wait to finally get some shade and hear the waves, cool down, etc. The grass is always greener.
If you look closely at a few "somebodies" who grew up and lived on The Harbor (and that includes the more inland towns like McCleary), they MAY be very, very likely to head eastwards than some regularly, all of their lives...or dreamed of doing such things all of their lives...and some of them may be just as or far more familiar with the wilderness areas in and around Cle Elum, Ellensburg, Wenatchee, etc. Not my cup of tea but it's the real deal for so many of my surrounding Harborites.