...How so exactly? Every circumstance I can think of in which a human limb could be struck by a billhook or brush axe, the same would occur with one of those tools if you were to perform the same motion with the tool swapped out.
This statement tells me you're only looking to promote your own inherently unsafe stuff. Get with the program; tin and green horn (but enthusiastic) axe and knife buyers of today are more likely to hurt themselves with a manual can opener than a seasoned tree topper 100 feet up on a springboard chopping through a fir was in the 1920s.
Sandviks are infinitely safer than open and long blade implements.