Google can be very difficult when it comes to approving add-ons for their add-on store as well. They approved my add-on that blocks porn ads on a certain website, but won't accept a trivial update on the grounds that it is too NSFW.

They make you provide a screenshot to submit an add-on. I used a screenshot of the website it works on with the porn ads it blocks heavily pixelated. I can't think of any other way to take a screenshot of what my add-on does. So I guess users will have to do without the new update.