I think there is a fundamental issue here in the history that is causing confusion. The originators of the AGI term did in fact mean it in the context of narrow vs general AI as described by OP. However they also (falsely!) believed that this general if mediocre capability would be entirely sufficient to kickstart a singularity. So in a sense they simultaneously believed both without contradiction, and you are both right about historical usage. But the events of recent years have shown that the belief AGI=singularity was a false hope/fear.
I think there is a fundamental issue here in the history that is causing confusion. The originators of the AGI term did in fact mean it in the context of narrow vs general AI as described by OP. However they also (falsely!) believed that this general if mediocre capability would be entirely sufficient to kickstart a singularity. So in a sense they simultaneously believed both without contradiction, and you are both right about historical usage. But the events of recent years have shown that the belief AGI=singularity was a false hope/fear.