NO

1 decompositions
 #1 -----------
   1: b(a(a(x1))) -> a(x1)
   2: a(a(a(x2))) -> b(b(b(x2)))
   3: b(b(x3)) -> a(b(a(x3)))

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