The point I'm getting at is that at the end of the day, rail is rail. Comparing LRT to metos/subways to double decker commuter rail is like comparing a sub-compact to a mid-size to an SUV. It is all determined by the vehicle used, and like with cars, there are plenty of grey areas (a Prius might be classified as a compact, but some of its dimensions are comparable to much larger vehicles).
So with Eglinton, seeing that it is underground and its trains will have similar dimensions and capacities to the metro trains on Sheppard, it is a subway. However, because the trains are also of a premium design to allow street running and the tunnels have to be extra high to use overhead wires, it is a subway with a lot of gravy on top.