I know this is an old topic but i wanted to write this for new users of the PX5s who might be browsing over old forum topics. Like me right now.
I believe the action in the video is Casio's attempt at replicating the "escapement" feature found on acoustic grand pianos (not uprights). Here's a YouTube video that explains a grand piano's action. The escapement feature is shown best from about 2 minutes in to the video.
Roland advertise this feature on their FP30 digital piano. I never even noticed it when i had my PX360 but i'm getting a PX5 tomorrow and wasn't aware that it had this feature because Casio didn't advertise it as a feature!
So while it's not 100% accurate, it's a very close attempt at replicating a grand piano's entire action.
