Hi and thanks for your question
The separate stages come from the Empire State Trails website.  I am currently adding in the details taken from those 28 stages from Buffalo to Green Island and have currently completed to Rochester.
The Empire State Trails website gives the structure or sequence that I am following.  OSM, when discussing walking, cycling and other routes suggests WayMarkedTrails.org is a useful browser tool.  
From my limited observations so far, on the ground there is only the circular Empire State Trails marker with indicators for direction – arrows that point ahead, left etc.
Here is a link that shows the four regional groupings from the EST website.  
https://hiking.waymarkedtrails.org/#route?id=11486087&type=relation
On selecting “Sections” you should see a structure to the information shown.  
EST = Empire State Trails – the source of the information
H = hiking
Erie Canal in clear – the three letter acronyms (ECa for example) that follow indicate
EC = code for Erie Canalway
a = Buffalo to Rochester
Selecting any one of those four sections will display the stages that EST show in their website.
On selecting ECa and then “sections” you will see your example of ECa08 amongst others.
Here is a direct link for the Brockport to Rochester stage
https://hiking.waymarkedtrails.org/#route?id=17814735&type=relation
This faceted code (ECa08) enables the structure of the Empire State Trails website to be emulated in Open Street Maps.
A limit to any faceted code in OSM is the upper limit of five characters that WayMarkedTrails will display.
At a big picture level, ADT American Discovery Trail, as shown in OSM, goes some of the way to using a faceted coding structure.
I hope that answers you question as to where the example you gave fits into a bigger picture.
Best wishes
