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Not sure about the pop. I tend to say no, this won't be the problem; however, there might be some reason the Onstar is popping due to no serial data input from the BCM.

Two class two wires come in on the brown (large) connector, terminals A1 and A2. One class two wire comes in on Pin G of the smaller black.
The wire on Pin A2 is the serial data wire to the radio from the BCM, and is used to communicate between the BCM and the radio, and also from the Onstar and XM modules. The wire on Pin A1 is the pass through wire from the radio to the Onstar module; the wire on Pin G is the pass through wire from the radio to the XM module.

So, Peripheral, before they made the change (which was to jumper the three wires together on their side of the adapter connector), required you to take the three wires going into the back of the two connectors, and splice them together. This way, the BCM still sees the three modules.

If you use the XM antenna for the new Pioneer XM module, a code will be set in the BCM that states the XM has lost antenna signal (something to that affect). It will not turn on the light, but if your vehicle is worked on by a tech, and he scans for codes, these codes will appear.

In addition, under some circumstances with some adapters; not sure which ones. To reprogram the BCM, if ever necessary, the radio fuse has to be pulled. Some of these adapters send out a radio message every so often, to let the BCM know the radio is there; however, some of these adapters constantly send out the signal, and confuses the BCM. I was able to load the new BCM calibration into my H3 without any problem. But I have heard, in some cases, the radio fuse might have to be pulled to program the BCM.