Per the current Washington Sport Fishing Regulations
, page 1:
State licenses and rules apply on National Forest lands.
Per the Gifford Pinchot NF website
Olympic National Park
Anglers over age 15 must have a current Washington fishing license!
Recreational licenses are required for both residents and nonresidents 15 years of age and older. Reduced fee licenses are available for qualified disabled persons, disabled veterans, youth age 15 years and younger and resident seniors (age 70+).
Fishing regulations are determined by the state: Washington Department of Fish and Wildlife
(not Olympic National Forest) requires a WA license only for saltwater fishing Mt. Rainier National Park
(there is no "Rainier National Forest") does not require a license but otherwise follows Washington state rules.North Cascades National Park
Fishing anywhere in the North Cascades National Park Complex is subject to all WA State fishing regulations and requires a valid Washington State fishing license.
US National Forest rangers do not enforce state game laws, so don't really care if you have a license or not. You'd think they'd know what's on their own website, though! Were you by chance talking to a clerical employee or a volunteer instead of one of the ranger staff? They wear the same uniforms, so it's hard to tell. Judging from the inaccurate trail info I've gotten from USFS ranger stations in Washington and Oregon over the years, the misinformation you were given is par for the course. It's only if you get really lucky and happen to talk to the trails coordinator or wilderness ranger that you can find out anything.