Was each order established by one Herald? In any case, it doesn't necessarily conflict. I don't think we have quite enough information to figure out every detail just yet.
I agree we do not have enough information, my guess would be that though it might be tied to the Heralds, that it might also be tied to what type of Spren that they are attached to. Which may have been originally determined by the Heralds.
We know that Syl is a binding Spren, and an Honorspren.
Nahal: Definition
The name Nile (Greek: Neilos) is thought to be ultimately derived from the Semitic Nahal meaning "river" from which the Hebrew nachal is derived
-to lead or guide to a watering place, bring to a place of rest, refresh
-carry, feed, guide, lead gently, on
-A primitive root; properly, to run with a sparkle, i.e. Flow; hence (transitively), to conduct, and (by inference) to protect, sustain -- carry, feed, guide, lead (gently, on).
Heb. nahal, in winter a "torrent," in summer a "wady" or
valley (Gen. 32:23; Deut. 2:24; 3:16; Isa. 30:28; Lam. 2:18;
Ezek. 47:9).
Nahar, a "river" continuous and full, a perennial stream,
as the Jordan, the Euphrates (Gen. 2:10; 15:18; Deut. 1:7; Ps.
66:6; Ezek. 10:15).
http://tinyurl.com/2fp292aThe Arab root nahal has the meaning of quenching ones thirst. the noun manhal - a watering place in the desert.