NO

2 decompositions
 #0 -----------
   1: c() -> a()

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

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