NO

1 decompositions
 #1 -----------
   1: h(a(),a()) -> b()
   2: b() -> c()
   3: f(f(h(b(),a()))) -> a()
   4: a() -> b()

unjoinable peak
    f(f(h(c(),a())))
*<- f(f(h(b(),a()))) ->*
    c()