Nah, the ofuda have commands written on them. Generally with no commands they regain some of their mind and/or go berserk (eg. when Yoshika's charm was removed she started writing poetry again without realising what she was doing), but in some depictions they need to be commanded to not be a corpse at all times.
Actual myth:
The Jiang Shi is the base lower soul left in the body after death. It only has feral cunning, hunger, lust, wrath, you know, the inner beast. The thing is such a soul with an already dead body is practically unstoppable by brute force, they can be horrendously fast, if stiff, and similarly strong.
The Taoist controls(or restricts, for weaker priests who can only barely suppress the body's instincts) its activity with the Ofuda. This replaces the missing higher soul with a set of instructions and programming. Losing it means they revert to their feral state and do whatever. However, they can also become possessed, without an Ofuda sealing it, a ghost can just dock right into the corpse for a joyride.
They are often blind, but can sense Chi(aka life force) through the breath. They feed on this or living flesh, they can kiss and suck out all your life. The more of it they have the more lively they look, and the better they fake being alive, as well as control their instincts. Also more powerful of course.
They can be stopped by fire, or complete dismembering, though there are a few other methods that can distract it using its lower soul(which again is based on the basic instincts and pretty easy to distract).
Finally, making it an initiator seems to take away quite a lot from it's actual talents.
