One benefit of having an IP Iteration every PI is that it creates an estimating buffer for meeting PI objectives. PI objectives are a set of SMART goals that align the teams and stakeholders to a common vision and mission for the upcoming Program Increment (PI). They are derived from the business context, priorities, and dependencies, and are agreed upon and committed by the teams during PI Planning1 However, since PI objectives are based on estimates and assumptions, there is always a degree of uncertainty and variability in the delivery process. To account for this, SAFe recommends that teams reserve 10% of their capacity for each PI as an estimating buffer. This buffer is used during the IP Iteration, which is a unique, dedicated iteration that occurs every PI and provides dedicated time for innovation, continuing education, PI Planning, and Inspect and Adapt events2 By having an IP Iteration as an estimating buffer, the teams can improve the predictability and flow of value delivery, as well as reduce the stress and pressure of meeting the PI objectives23 (Must be taken from SAFe 6 Scrum Master resources) Reference:
PI Objectives - Scaled Agile Framework
Innovation and Planning Iteration - Scaled Agile Framework
SAFe Scrum Master Course Outline