NO

1 decompositions
 #1 -----------
   1: a(a(x1)) -> b(b(b(x1)))
   2: b(b(b(b(x2)))) -> a(a(a(x2)))

unjoinable peak
    a(b(b(b(x1))))
*<- a(a(a(x1))) ->*
    b(b(b(a(x1))))