I noted the strap flapping around wildly underneath.
The rattle sounds more like the strap catching the casing.... I don't think I'd be putting a camera to the shake test in that fashion .
Also be aware the lens opening and shutting creates a vacuum of a kind easy entrance for minute dust particles.... you'll soon be sending it in for servicing should the dust fall on the lens or the CCD then you won't be happy,
The camera works or it doesn't cameras and are not supposed to received sudden shocks, your lucky it's still working.
The camera has an optical image stabilizer. You can get almost any lens with optical image stabilizers to "rattle" if you shake them hard enough.
The stabilizer system uses a motion sensor (gyro) which powers up as soon as you start to press the shutter button (the moment when the camera has to meter and focus). If the sensor detects motion, it responds by shiifting some optical elements inside the lens to compensate.
When the camera either is not powered up or not using the image stabilizer (e.g. you are not trying to take a shot so the image stabilizer shuts down to save power.) it's often possible get these lens elements to shake and rattle.
This is not a defect. Most any lens with built in optical image stabilization would do this.
I usually have to roll my eyes whenever I see someone post such a video ... why would someone deliberately abuse a product... subject it to something it would never encounter under normal use... and then attempt to claim some flaw or defect?
This is sort of like the old joke:
Patient: Doctor it hurts when I do this with my arm.
Doctor: Then stop doing that with your arm.