Suppose a robot with a flat surface pushes cones into a neutral corner such that they are totally and equally accessible to both alliances such as in this picture, would this be considered to NOT be a violation of SG9 since there is no “hoarding” involved as defined in the following Q&A answer about SG9 (miss identified in the question and answer as SG6):
As explained in this Q&A response and in the corresponding referee training video, one of the criteria that referees should watch to determine if an alliance is hoarding or not is if the Cones in question are being actively kept away from the opposing alliance.
If the hypothetical alliance in your question is just moving the Cones into this corner and not protecting them or otherwise restricting access to the opposing alliance, then yes, this would be legal.