No, definitely not "most efficient". Nature is only rarely extremely efficient at any one thing, but given the complexity of the environment nature (through evolution) has managed to be "good enough" at a wide variety of things -- often using tradeoffs that we fail to see even after looking a thousand times to deal with issues we have not yet begun to fathom. You're right that many millions of generations, through evolution, can often find ways that are "more efficient" than what we humans have thought of in a just a relatively few iterations so far.
Believing that the "path" something in nature discovers is "most efficient" is pure unfounded faith and it is a grave mistake to "believe" that there is not some "more efficient" way to do something; with all the the ifs ands and buts all hanging and hinging on defining what is most important to any given circumstance at any given time.
BTW, comparing paths found between arbitrarily spaced nodes on an otherwise featureless medium decries all the issues of geography, physics, engineering, economy, personalities, and even other simple historical influences (the latter two of which would be next to impossible to model), in the creation of a rail system in the real world, and thinking that the former is better in any way than the latter is the height of hubris based on unscientific belief systems.