If you are building a piece of software that is The Software that your user will be using most of the day, I think this is good advice. But there is tons of enterprise software that this doesn't apply to:
* When the primary users of enterprise software are in high turn over jobs, they are unlikely to develop expertise in your tool.
* When users need to use once a month or once every six months, they won't be able to develop expertise in your software. Think about HR systems for updating contact information (which only happens at major life events) or updating benefits (which happens during open enrollment once a year, or during major events). Or maybe a portal you log in once per month to pay a bill.
* When your software is used often, but it is one of many tools that your users context switch between, they are unlikely to develop expertise in your software. The switching between different pieces of software means that there isn't enough time for things like muscle memory for keyboard shortcuts to develop.
Enterprise UX design, like all UX design, should start with understanding the customers and their needs.