At GTR-C there was no readily available resources to repair or create new low bar flaps, and 2 out of 3 were damaged pretty early in the day (they received a good amount of damage on Thursday as well). Matches were run with both flaps removed to ensure an even playing field.
From the existing game rules as well as Q&A answers it is, in my opinion, fairly clear that the GDC did not intend to allow any circumvention of "carrying a single ball through a defense" method of getting balls into the courtyard. Whether that be through the opponent's secret passage, launching over defenses, or a robot moving the low bar flap out of the way. I think considering the GDC's intent, it is pretty clear that if the low bar flaps are removed, they would not like human players being allowed to bowl a boulder directly into the opponents courtyard.
In fact, I would argue that the entire point of the low bar flap as well as the lower bar, was intended to prevent this scenario. Therefore, I think it's reasonable to award a Tech Foul for the action. This is the same foul a robot would receive if a robot were to do this. Allowing bowling under the low bar would make boulder starvation much easier and possibly significantly change the game.
As far as unfair awarding of Tech Fouls, as soon as the flaps were removed, an announcement was made regarding the new rule (more like an amendment or clarification imo). Even if teams didn't hear (or flat-out ignored) the announcement, a good deal of leniency was given to human players in regard to the Tech Fouls.
The field crew had already been having problems with boulders getting stuck in the sensors of the low goals and had the referees who were on break stationed behind the towers to rectify the situation (as well as ensure there weren't more than 6 boulders at any time). After the flaps were removed, these refs were instructed to remind any human players vigorously bowling boulders that the next attempt would result in a Tech Foul. Any Tech Fouls received after this change should have been from a human player who was previously warned. Of course, that is near impossible to monitor, but I had seen refs warning HPs even in the last few matches of the day.
It's definitely a difficult situation that is not easy to deal with, but I think the team at GTR-C did the best with what they were given, and did it in a way that would satisfy the GDC and the spirit of the game. If anything, it raised the skill requirement of the human players as there was a sweet spot between the boulder staying in the secret passage and rolling under the low bar
.