This reports the sysUpTime at which the currently selected output nodal hierarchy list was chosen by the decision process. An admin uses this to know how long the current output hierarchy has been stable, noting it only updates when the decision process's chosen result actually changes, not on every decision process run. For example, this timestamp staying constant across several pnniDecisionProcessTimeStamp updates would indicate the decision process keeps re-selecting the same output hierarchy rather than switching to a different one.