https://www.portseattle.org/sites/de...02021%29_0.pdf
Here's a link to the Port of Seattle parking policies. I unfortunately let my parking lapse as I opted for time off and didn't need to pay the monthly fee. Had I continued to do so I'd be grand fathered in. Would have been nice to know that losing the parking came with saving money for several months. Anyway this link to their policies spells out clearly why they have decided to limit it to just domiciled employees.
I did some research and found the above link, DirectToEntent. So now I know how you're getting parking. Don't miss a payment would be my advice if paying month to month.