Any output from a planning process is a consequence of the approach applied by the planner to develop their plan. Different people will develop different plans to achieve the same objectives based on their knowledge, experience and attitudes. This influence can be ignored or, if better understood, exploited!
This article outlines the fundamental principles and philosophies that can be used by planners to develop their plan: https://mosaicprojects.com.au/Mag_Articles/AA001_philosophies_of_planning.pdf
For more papers on schedule strategy and design see: https://mosaicprojects.com.au/PMKI-SCH-010.php#Process3