Voadam
Legend
I assumed when WotC had that type of language in 3e clerics it was to continue with the TSR 2e non-deity full spellcasting priest of forces and philosophy line that had been going for about a decade since Complete Book of Priests.I don't know if anyone has brought this up, but I just assumed WotC had added in the "believe in a source instead of a specific god" because some tables don't want to deal with the religious subject at the table and it was an "out" for these groups. I know that getting into aspects of worship and religions is something several of my gamers would like to avoid and that has been why I've allowed the Power from Forces for characters instead of the "Pick a god and stick with it" method.
Narratively the forces and philosophy clerics fit in with my memories of Fred Saberhagen's Sword novels where they had things like the Red and Blue temples which were big power organizations separate from the gods.