Read: "When warforged are even considered." Note that Psiforged Body is in an EBERRON book, thus mention of psionics there prompts attention to warforged.
Here on the forums we have, at the least, Rageforged (barbarian rage) and Soulforged Body (incarnum). That's three, the rule is satisfied, ergo subsystem goes hand in hand with warforged "body" feat.
On the other hand, this is a 3.x project, so regardless of whether my insane logic or lack thereof is followed I'll never be able to use this.