To the letter, it is in fact goaltending, because the robot contacting the ball makes the ball count as 'part of the robot,' and clearly the balls would have to be in downward flight (unless they were bounce-passed or something). It's also clear however, that the balls were not intended to be scored, and to any reasonable person, it's a no-call. FIRST has purposely been vague and ambiguous here so that refs have a bit of leeway; they make no mention of human player or robot driver intent, meaning that refs can do what they think is appropriate. There should probably be a rule saying the refs can judge the intent and it's at their discretion to give penalties on that basis, which would eliminate the disparity between calls of this nature (i.e. one ref might give a penalty for this occurence while another might not). But we're engineers, not lawyers, so that would be a waste of time, because we all knew what FIRST meant.
