Is Defense A Great Strategy?

Your interpretation is not correct.
This situation has been answered.

Basically, if the defensive robot is trying to stop the offensive robot from scoring into its own zone, and got pushed to the starting bar, the defensive robot will or might be DQ.

If the offensive robot, with no intention to score, but pushed the defensive robot to the starting bar, then the offensive robot will be at fault.

Trust me… when come to high stake matches, you dont even want to be in a situation that requires the referee to decide if it is match affecting or not.

Now, I am not against defensive robot, in fact, one of my teams had a wallbot during Singvex, but I still think there is no point having a pure defensive robot this season.
For this season, I just can’t see how a purely defensive robot can guarantee a win (during Worlds eliminations rounds).

Not sure if I have understood you - are you referring to stacking cones on the mobile goals in front of an opponent’s mobile goal?
If yes - then it might cause a mild inconvenience for the opposing alliance, but it won’t be a deal-breaker.

If you are referring to just putting the cones on top of another cone in front of the opponent’s mobile goal, then by definition, the cones are not stacked.