In the PNW lowlands, we get so little snow it really doesn't matter. It just takes one event to define the whole winter. Even the worst winters could randomly deliver in a single day, and you wouldn't even know. Anafronts and convergence zones can drop snow even with non-arctic setups that don't even look remotely close to good at the 500mb level.
The entirety of an El Nino +QBO can be absolutely horrendous, but it just takes one week to change everything.
The same thing happened this winter for Seattle. Randomly got snow in March, despite the pattern still remaining largely miserable.
2018-2019 was more of the same. Winter was garbage but quickly turned around towards the end.
The only good configuration in the PNW is La Nina and +QBO, for more consistent cold and locked in average or above average snowfall. Everything else is a wild card when your average snowfall is literally 4-6 inches.
Decadal oscillations don't exist? There are a lot of long term configurations that cause patterns to get stuck, and that always happened.
We had "bad" and "good" stretches of winters in the past too.