Share? It is entirely the unit's fault. (I'm including mine here.)
For example, I can't possibly give you the benchmark for your Librarian. I don't know what your space is like, how much literature you purchase, what the hand-me-down culture is of your scouts, your proximity to the scout-shop, you budget for a half-dozen electronic tablets, if you're all about the paper, if you need to build shelves, or lockers, or mobile storage with solar panels for recharging. Maybe you need a bevy of pamphlets. Maybe you need sheet music for your buglers and musicians. Maybe your honor guard needs a collection of historic flag pamphlets."" I don't know. If I don't know any of that, how is National gonna possibly know? Figure out your own stinking benchmarks. Set them.""
We developed a general set of benchmarks for all the positions in our troop. However, the expectations (benchmarks) are purposely set a bit generic because we ask each scout to define his own set of benchmarks that his will use to measure his performance. He writes his benchmarks in his book so that he and the SM can refer and discuss them later. We do that because benchmarks change as the unit grow and mature, and to tailor the benchmarks to each scout.
BUT remember, growth is developed in the journey, not the destination. Sometimes scouts find they aren't very good with the particular responsibility. I have had many scouts grow considerably in character while failing to meet some of their benchmarks.
I guess what I'm trying to say is for me, expectations (benchmarks) should be more of a guide for the SMs than a check list.