We are not going to be able to provide a blanket answer that encompasses all hypothetical Robot-to-Robot interactions of this type. The best way to approach this question is going to be to look at the broader context of G12 beyond the portion that was quoted.
<G12>Don’t destroy other Robots. But, be prepared to encounter defense. Strategies aimed solely at the destruction, damage, tipping over, or Entanglement of opposing Robots are not part of the ethos of the VEX Robotics Competition and are not allowed. If the tipping, Entanglement, or damage is ruled to be intentional or egregious, the offending Team may be Disqualified from that Match. Repeated offenses could result in Disqualification from the entirety of the competition.
c. A Team is responsible for the actions of its Robot at all times, including the Autonomous Period. This applies both to Teams that are driving recklessly or potentially causing damage, and to Teams that drive around with a small wheel base. A Team should design its Robot such that it is not easily tipped over or damaged by minor contact.
d. Game elements in possession of a Robot are an extension of that Robot. Therefore, Entanglement (e.g., grasping, hooking, attaching) with Cubes that are in the possession of an opposing Robot is a violation of this rule.
G12 is not intended to be a "don't play defense" rule; it is a "don't destroy other Robots" rule. This core principle should be obvious - VRC is not Battlebots. However, VRC games are designed to encourage Robot-to-Robot interactions, so there is always a possibility of an interaction which results in a Robot being destroyed, damaged, tipped, or Entangled. G12 then exists to provide guidance for a Head Referee to walk through when determining whether that damage should result in a violation.
It seems there is a strategy where teams will ram, or spin into other tray-bots in an attempt to knock cubes out of the trays of the other robot. This seems to be a direct violation of G12d, and G13 would also be in effect since offensive robots get benefit of doubt.
Since Entanglement is not occurring, G12d should only be used as the general guideline that Cubes are an extension of their Robot. So, picture this interaction as if the Cubes were just square metal mechanisms resting on a Robot.
- Bumping into opponents is not illegal in itself. However, there is a threshold where bumping becomes reckless ramming, and could be considered a violation of G12, S1, or G1.
- Dislodging parts of your opponent's robot (without Entangling them) is not illegal in itself, because part (c) puts some responsibility on the opponent to design their robot such that it is not easily damaged by minor contact. However, there is a threshold where incidental damage becomes intentional/egregious destruction, and could be considered a violation of G12, S1, or G1.
The only pure grounds provided in the Game Manual for a G12 violation are "destruction, damage, tipping over, or Entanglement [...] ruled to be intentional or egregious". Ultimately, whether something is "intentional or egregious" is a line that cannot be drawn rigidly in black-and-white; the need for contextualized interpretation of this threshold is why VRC relies upon the in-Match judgment of human Head Referees. We cannot make rulings from afar or provide answers for every possible hypothetical scenario; we can only implore Head Referees to make their best personal judgments based on the rules as written, and provide as many guidelines as possible via the Q&A.
As a Head Ref, he wants to be able to have teams ready for the game when they get to Worlds, but based on past experiences, the game is played much more defensively at Worlds than what we played in our region throughout the season. When this happens, as a volunteer he feels as though he let the kids down and did not properly prepare them for the Worlds in which they qualify for.
A volunteer Head Referees' primary responsibility should be to interpret the rules as written and as the context of their event necessitates. If a game is played more defensively at a different event, then it would stand to reason that the judgment calls would be handled accordingly in the context of that event.