If you're autoupdating Chrome, you have to get in a habit of checking the settings menu periodically for new stuff. Unlike the more mature FireFox settings menu, Chrome's is still getting additions.
This appears to be just be turning flash on or off globally (and not very quickly either). FF has that level of control out of the box as well.
http://www.chromeextensions.org/appearance-functioning/flash...
the only difference that i know between this and what you explained is the lack of a placeholder image.
https://chrome.google.com/extensions/detail/gofhjkjmkpinhpoi...
In fact, I don't think it really can work in any real sense as an actual blocker since chrome doesn't provide an API for that. As I understand it, the best it can do is to remove the flash after the page has rendered.
https://chrome.google.com/extensions/detail/cdngiadmnkhgemki...
But what you've said is true, FF's FlashBlock has much better control over Flash because of the control it has via the API. Chrome doesn't offer the same level of control to extensions, so they're all just going rewrite the page on load. That's been good enough for me though.