The rigidity is the expensive part. Modeling has gotten easier with parallel distributed computing. Reliability is of qualia that I would only attribute to platinum group metals. If heat causes errors in an organic synthesis, then that reaction mechanism is not selective enough for the desired purpose. The flexible bonds in biopolymers serve as counterpoint to the notion that bond rigidity is essential to stochastic nanotechnology. On the contrary, self-assembly requires some bond flexibility.
Rigidity helps you for the same reason using a jointed arm is easier than controlling a tentacle. Limiting the number of degrees of freedom can make things a whole lot easier.
Yes, there are interesting designs with biopolymers, but they probably cannot get you the type of atomically precise manufacturing that you need for most "cool" MNT applications.
It isn't fundamentally easier to control an arm than a tentacle; That is human intuition based on the fact that we have arms. Limiting the number of degrees of freedom is something done at the level of experimental design for the production of chemical libraries. DNA is already a programmable medium for nanorobotics, and skilled genetic engineers can do atomically precise peptide biosynthesis for the sake of NMR spectroscopy. It does not seem as though you are informed of bionanotechnology in the present.
Octopodes do not beg to differ, they tergiversate to genuflect.
The thing to recognize is that tentacles predate arms, legs, or fins by millennia. Jellyfish tentacles have fewer kinds of parts than any arm, hence they constitute simpler machines.
In the paper you cite, humans are describing cephalopods with a model based on their own anatomy; it is not the other way around, as you claim.
