Yeah I think it's ridiculous that the ACA route doesn't actually include the WA Pacific Coast. I've lived in WA for 40 years and have been out in the peninsula throughout that time and just can't agree that there has been major changes there that has suddenly made it "tourable". The services have remained the same (if towns have grown of course) and are pretty reasonably space out. The WA coast is a far more rugged and wild coast then the tame (though wonderful) OR Coast. Only very Northern CA coast compares and is of course different. And while there are plenty of places where the route ducks in from the coast it's not like you are riding on the beach the whole time on any stretch of the coast. Not to mention there is a distinct difference between the northern and southern stretches of the coast and on the southern end you are pretty close to the water for long stretches if you use 105, 109 as well as 101.
Finally even if you want to take the inland route along the Sound and Hood Canal at the very least the Coast Route should from Elma (where WA Parks inexplicably starts) take the back roads and 105 to the Coast at Twin Harbors State park and down the coast and along the bays to Cape Disappointment. There is great views, great parks and great riding on this stretch and this isn't part of WA Parks, so no way to do all of the WA coast on ACA rates... Why anyone would want to take the inland route near I-5 (which does have some nice places, but just doesn't compare) beyond being in a real hurry, is bizarre to me.
In my opinion you haven't "ridden the Pacific Coast" if you don't do the WA section and I always recommend people to use the Kirkendall and Spring
book along with the ACA maps for this reason.