For each observation iNaturalist keeps 2 dates: Observed and Submitted. In the New Life List “All Observations” are sorted by “Date Added” which (in cases where observation and submission are sufficiently apart) is apparently not the submission date but the date of the observation.
An example is my observation https://www.inaturalist.org/observations/39759076 which was observed in 2005 and submitted in 2020 and which gets to the first place when sorting the observations by “Date Added, Oldest to Newest”.