If you're going to be critical of everyone, the document doesn't state you have to be family, just residing at the same premises.
Given where it's buried and the little chance anyone has of actually finding and reading it, I'm not surprised that people aren't adhering to it. I only found it because of the web address in your linked document (so I knew I had to go to the WA Gov website). No-one else is going to find it if it's not publicised in the news somewhere. I've done several searches using web browsers and still can't find anything other than the >10 person restriction on outdoor PT activities.
Yes now it's been properly published but the <2 or =2 situation conflicts.