My understanding is that chutes are packed with great care since they're the only thing stopping one from going "splat!"
I could believe that it's an intentional fake, maybe, but unintentionally packing a good-sized rock seems unlikely... although, I guess it's not as improbable as a meteor sailing past your head while you're skydiving!
It's probably not a fake or packed inside the chute, since he was under canopy for some time when this occurred. Low odds are not zero odds, but then again, it can be a clever April fools segment.
Also, chutes are not packed with great care. A main (the parachute you generally use) takes an experienced packer 5-10 minutes to fully pack and some people hurry through it to get on the next load. Outside of two things you need to get right (make sure the slider is up, make sure lines aren't over the fabric), it will open. Most of the packing is all about reducing the pack volume and slowing down the opening, not ensuring it.
A reserve however (the second chute sport jumpers wear), gets packed by a certified packer and gets re-inspected and repacked at least once every 180 days.
I could believe that it's an intentional fake, maybe, but unintentionally packing a good-sized rock seems unlikely... although, I guess it's not as improbable as a meteor sailing past your head while you're skydiving!