I cannot guarantee that it's working properly. The feedback code is closed source, and I know it also does some data gathering to include technical info about the router in the report, no idea if that part works as well.
And Asus may very well decide to dismiss any feedback that does not come from a stock firmware, to avoid wasting their time in chasing after wild gooses. I know that personally I generally ignore any "bug report" that comes from anyone not running my firmware. Too often I wasted time trying to track down something, only to discover later on that the user was running someone else's forks, they weren't running my firmware, or they were running an older version.
People should not use that page on my firmware, period. The only reason I left the actual web page there is for a while some third party developers were reusing that page to add new content to the webui. Now that the new addons API has been available for a while, I am seriously considering completely removing the page if there are people found to be misusing it.