NO

2 decompositions
 #1 -----------
   9: .(.(x2,x1),x3) -> .(x2,.(x1,x3))
  10: .(x2,.(x1,x3)) -> .(.(x2,x1),x3)
  11: .(a(),.(b(),a())) -> .(.(b(),a()),b())

 #2 -----------
   1: +(x2,x1) -> +(x1,x2)
   2: +(+(x2,x1),x3) -> +(x2,+(x1,x3))
   3: +(0(),x2) -> x2
   4: +(s(x2),x1) -> s(+(x2,x1))
   5: fib(x2) -> :(x2,+(fib(x2),fib(s(x2))))
   6: *(x2,x1) -> *(x1,x2)
   7: *(0(),x1) -> 0()
   8: *(s(x2),x1) -> +(x1,*(x2,x1))

unjoinable peak
    .(.(a(),b()),.(.(b(),a()),b()))
*<- .(.(a(),.(b(),a())),.(b(),a())) ->*
    .(.(.(b(),a()),b()),.(b(),a()))