The Lean tool-heads insist that work should be standardised. This is where they get this guidance:

The work process itself, along with the management process, must be absolutely standardized by managers, and by manufacturing and industrial engineers as well, before a work team can have any hope of improving it.

Standardization in this context means creating a precise and commonly understood way to conduct every essential step in every process.

(Womack, J. P., D. T. Jones and Roos D 2007 ‘The Machine that Changed the World’ Simon and Schuster, London p290.)

But standardising work in service organisations will prevent the system from absorbing variety.