Oh I'm sure they're required to knock before entering any room, even if there's no sign. It doesn't sound like you care that much, but I have a friend who runs in the fall half-marathon - Wine and Dine? - and she said she was able to request a time for housekeeping that fit her schedule.
I was afraid your "95%" comment would be interpreted by some to mean that Disney does not care at all about the Room Occupied sign, which I don't think is the case. It doesn't take much to set some people off on this topic.
Then some need reading skills. My 95% comment was that for most of the visits, I was in the room and didn't find it an issue.
Yes, it's the W&D Half in November. I do all three races that weekend, hence the getting up at 2:30 AM 3 mornings in a row to be on the bus to the starting area. I'll be there in 13 days for the Princess Half. Will certainly check if I can have Housekeeping schedule the check around 9AM. That way, when I get back to my room after the races, they've done their thing.