Yes, factory optional power antenna was on that side. That option did not exist until the model year your car was built, as the cars were designed to have the windshield antenna from the factory. If GM had offered a power antenna, it would have invalidated all of their promotion of the windshield antenna's performance. Plus, more room on the lh side than on the rh side.
Having said that, can't really tell if what's on top is really a factory antenna bezel or an aftermarket antenna. Need to check sales and parts/service literature for verification of what is what.
I suspect the whole power antenna availability was driven by the then-popular factory CB radios (with AM/FM and AM/FM Stereo variations). The antennas for the CB radio options had a center load in the mast to support improved CB performance. There were also aftermarket power CB antennas, too, plus non-CB versions.