As long as you ended up with about 30-35% of the original volume of liquid you should be fine. There is no need to chop up the leaves, just that it is best to cut the leaves and stems so that they fit inside the pot without having to fold them.
I have never had the "oleander soup" extract I have made, nor have I seen any made by anyone else, have a consistency of chicken soup. Why the guy who first figured out a recipe for the extract based on the original Ozel patent for Anvirzel came up with the term "soup", I don't know. It is not soup and should not be consumed like soup (a bowl or cup at a time would be far too much). But that is the name he chose and we have been stuck with it ever since.
Once properly strained, the consistency is not much different than tea and neither is the color. Do be sure to strain it very well.