Kudla and Nurlutta used to be step downs like Glenalta and Pinera; the latter were complete with train stop indicators.
I have a vague recollection that Greenfields used to be called Parafield but will cede to greater wisdom on this if required. It was a step down.
Greenfields is a relatively new station at the south western corner of the Parafield Airport and one I used quite often going to the (then) SAIT Levels Campus.
There are quite a number of houses in the area and I would assume the station was built to cater for these. For a time it was a bus interchange point.
Pedestrian access to Mawson Lakes is problematic since developments tend to be self-contained with no thought to movement between the 2. There was a track to the Levels campus constructed in the late 1970s complete with its resident magpie who defended his tree (there was only one) with great vigor.
This track ran parallel to the railway to a bridge over the creek, then directly across the paddock to the SAIT. This track could form the basis of a path between Greenfields and Mawson Lakes were it still intact. It seems years since it was useable.
Parafield is at the northwestern corner of the airport.