Simple TTL will still have the camera send an 'off' signal to the flash when proper exposure is met. Doesn't seem that complicated.
Fact is that simple TTL uses completely different signaling compared to i-TTL, and some fancy new flash trigger might not bother supporting it. Note that simple TTL is usually unsupported with digital cameras and the Phottix data sheet explicitly says it supports digital cameras.
Trying to be the best of whatever I am, even if what I am is no good.