But no one in their right mind would do that.
I have also seen this and I'm pretty sure I've seen a video of someone doing this.
Just because someone can afford to buy a tractor, it doesn't mean they have the common sense and/or understanding of the basic laws of physics to use it properly, hence the endless array of product safety labels on virtually everything. Even when people think they know what's going on things can still go very wrong.
I thought I knew what I was doing when I first used my Jinma loader. I'm a pretty careful person as I work with some very dangerous things on a daily basis. I was lifting and dragging the backhoe crate with a strap. Well the strap was just a bit more loose on one side of the crate than the other (I thought it would self equalize) and when I began to lift the end of the crate to drag it, the tractor instantly flipped up onto two wheels and very nearly went completely over.
It flipped from left to right not back to front. Ironically the unbalanced load caused the tractor to flip up onto two wheels but also kept if from going over completely. Luckily I was wearing the seat belt which kept me from be pitched off the seat, so I got it under control. Without the belt I would have probably been pitched under the ROPS and with my foot off the clutch it probably would have went all the way over on top of me.
Hindsight is 20/20 and afterwards I realized how lucky I was because no one was home at the time and didn't return home for another 5 hours. It could have been a very, very ugly accident.
I never would have believed the tractor would/could flip that quickly and easily while not moving and with the bucket that low.
Live and learn.
WEAR YOUR SEAT BELT EVEN WHEN YOU DON'T THINK YOU'LL EVER NEED IT!!!