Besides the filtering aspect mentioned Xert’s calculatiion of your power curve does not rely solely on MMP sampling.
Take a look at any of your past HIT activities and select the Power Duration tab.
Notice there are three lines. MMP for the activity, current signature, and calculated signature from the activity data.
On the flipside there are also situations where a bump in PP can occur if a max effort under fatigue is expressed that doesn’t jive with your current signature. For example, you hit 852 watts (for 5-7 secs minimum) when 838 was your predicted MPA at that moment. An adjustment to PP is warranted.
See: Is PP a theoretical number? - General - Xert Community Forum