Sorry for my late reply.
From my perspective the reasons seem to be mostly historical. In any event, I am pretty sure that at an actual competition any inference (whether caused by an ultrasonic sensor or anything else) would be dealt with and therefore would not really be tolerated. The reason why the rules do not mention it (and why it thus may look like such an inference would be tolerated) is that there historically were not many issues with ultrasonic sensors.
As my reply above suggests, the spirit of the rules is not to over regulate wherever possible. In this case, the local Organizational Committee would be called to resolve the situation. If it was my call, I would probably ask both teams to figure out how could they play together without affecting their opponents robots. If that was not possible, I'd probably ask both teams to turn off their sensors.
I would recommend using good judgment. If your sensors were not affected, I would assume there is a high chance other teams would not be affected either.
Sadly, I do not think that technical documentation of teams competing at the international competition is publicly available in general. As I see it, the best way of getting access to it would be reaching out to the respective teams.
This is something that should certainly change in the future and when it does, it will most probably be announced on this forum.
Please feel free to let me know if this helps.