There are several versions of the sharkfin antenna's guts actually. Mine had two "chip" style receivers, as well as a flat metal blade-type antenna that fit up inside the sharkfin part of the plastic housing. I've now seen two others that had no metal blade, and one only had a single chip for XM only.
Here's the guts from mine, note the flat blade antenna:
So, after a bit of research, IIRC, the pink colored chip is the Sirius/XM receiver's antenna, the grey is for GPS, and the flat blade is for FM Diversity which allows the stereo to cut to a smaller, ultra-low gain antenna when local stations are being overloaded from being to close to them. Interesting note, in Honolulu where I had my car audio shop decades ago, I used to install two antennas on customer vehicles when I carried a specific model of Clarion stereo. It had two antenna ports, one for "DX" one for "LOCAL", and it would automatically switch to the shorter antenna when one was in town. Worked okay for its time, but new stereos work much better than the old units like this!
Okay, FM 101 class is done, I'll shut the hell up now!!!