One possible explanation is using the parametrization of a cycloid. It is given by $$ x = r(t-\sin t)\\\ y = r(1-\cos t) $$ for some $r>0$. If $y = |\sin x|$ is a cycloid, or more generally, homothetic to cycloid, then it will be possible to find some constant $a\in \mathbb{R}$ such that $$ |\sin(r(t-\sin t))| = ar(1-\cos t) $$ for all $t\in \mathbb{R}$. However, it is not true.