Some people are born with only one arm. It is for this reason that we can no longer describe humans as having two arms. /s
Reminds me of Steve Jobs unveiling the first iPhone. He mentioned it doesn’t need a stylus, but something all of us are born with!
However, if it turned out that having two arms meant you were at a higher risk for a specific cancer, you would probably describe it as 'two arms leads to higher rate of X cancer' rather than 'all humans are at higher risk of X cancer' because it's burying the lede.