We don't have control over the sending and receiving process, unfortunately. All messages get received through the phone, by your system. Android controls the reception process, since there is such tight carrier integration. When Android gets a new message, it then notifies any SMS apps on your phone.
Similarly, when you are sending a message, Pulse SMS will hand off that message to your system, to make the carrier integration and send the message. Then Android will update the sent/delivered status of the message when it hears back from your carrier.
Pulse SMS doesn't control most of this process. The app is forced to rely on your device/system as all third-party apps do.
In addition, some carriers have begun implementing advanced messaging or RCS protocols that third-party apps cannot implement. For more info about RCS, please see this article.