ESRI mapservice layer features not loaded entirely when it loaded with L.esri.featureLayer. Features which are visible at a particular zoom level gets loaded and rest all not available for further processing. Only when zoomed out, the map extent expands and all features are loaded.
it is by design that esri leaflet's
L.esri.featureLayer only fetches features from a service that are located within the current extent of the map.
check out the sample below for an alternative example which uses
L.esri.query to make a request for whatever features you want.