Hi Frank, both of these are excellent questions. Thanks for taking the time to ask.

The principles we used for the Lightning Experience are indeed broad. There are a couple of reasons for that. One is that Salesforce itself is broad and encompasses products for marketing, service, an app platform, communities, IoT, mobile, and of course sales. We needed words that could scale across products, teams, third party partners, words that were easily communicated and understood. So far we’ve not found them limiting — there’s lots of room inside each one to push the envelope. Take efficiency for example. We could design a more efficient way to log a call by saving a click or two (incremental), or we could use the concept of efficiency as a springboard to reframe the task of call logging. How might we eliminate the need for people to log calls altogether? That could lead us to interesting places.

You’re correct that embracing the principles into a whole greater than the sum of their parts for a given design would be ideal. We strive for it every time. But we often bump into resource, time, legacy or technical constraints. We don’t get all the ponies. A priority order guides our rationale when making the necessary (and sometimes painful) tradeoffs.