YES

   3: or(T(),x1) -> T()
   4: or(F(),x1) -> x1
   5: or(or(x1,x2),x3) -> or(x1,or(x2,x3))
   6: or(x1,x2) -> or(x2,x1)

@Jouannaud and Kirchner's criterion
--- R
   3: or(T(),x1) -> T()
   4: or(F(),x1) -> x1
   5: or(or(x1,x2),x3) -> or(x1,or(x2,x3))
   6: or(x1,x2) -> or(x2,x1)

--- S
   3: or(T(),x1) -> T()
   4: or(F(),x1) -> x1
   5: or(or(x1,x2),x3) -> or(x1,or(x2,x3))
   6: or(x1,x2) -> or(x2,x1)


NOTE: input TRS is reduced

original is
   1: or(x1,T()) -> T()
   2: or(x1,F()) -> x1
   3: or(T(),x1) -> T()
   4: or(F(),x1) -> x1
   5: or(or(x1,x2),x3) -> or(x1,or(x2,x3))
   6: or(x1,x2) -> or(x2,x1)

reduced to
   3: or(T(),x1) -> T()
   4: or(F(),x1) -> x1
   5: or(or(x1,x2),x3) -> or(x1,or(x2,x3))
   6: or(x1,x2) -> or(x2,x1)