GM peak and hold injector

I saw an article that said on the peak and hold injector, both the B+ and ground are wired to the ecm? On my old pfi--saturated injectors--only the injector ground is connected to the ecm, not the B+. Why would the peak and hold injector receive B+ from the ecm, if it does? I understand there has to be a current limiting feature on the p/h injector circuit, but on this application, I thought the ground circuit controled it? thanks