Partially-agreed on the former, but not the latter. So long as the chain is not loaded near its tensile limit, then the grain boundaries that support the load

Partially-agreed on the former, but not the latter. So long as the chain is not loaded near its tensile limit, then the grain boundaries that support the load within each link do so in parallel and are therefore redundant. The selection of the allegory of the chain was intentional -- each link must be properly formed, or the entire chain will fail. If it breaks, it is surely correct to say, "the chain broke", but in truth, it was actually link-86. For JWST, the remarkable/audacious thing is that many links in the chain from launch to observation are potential single-point failures. Furthermore, many of them haven't ever been tested independently in space... ever. It is a hell of a triumph that JWST has gotten this far already. If even a small fraction of the instrumentation works at this point, we are going to learn a ton about the universe, simply due to JWST's position, collecting-area, and mirror-diameter.