It fits with what Lash told about herself when she still thought about herself as Lasciel. About all the countless souls she had seduced and destroyed.
It fits with everything else we hear about the fallen except for the lies their hosts tell themselves.
You are taking a traditional simplification of Fallen=demon=traditional demon.
Take Thorned Namshiel as a potential example. He's into magic. Is he responsible for "leaking" magic to mortals? Accumulating power for himself through the use of hosts for experimentation? What does he care if a host is vaporized in a magical experiment that even he can't rebuild them from if he learns something?
The point then wouldn't be making the host sink into ever-lower depravity, but in getting the host to fulfill Namshiel's agenda.
The idea that their goal is nothing more than reducing their host elevates the hosts in importance to being the point- that's classic Lucifer-aligned demon stuff. The Fallen are rebels. Not a unilateral team with united purpose and mission.
