It would be interesting to see on TV a custom officer state that a giant puppet is dangerous for Canadian security. It would also be interesting to see signs showing basic demands such as free speech, human rights, democracy being stopped as a threat to Canadian government. They rent the ski equipment. For many activists the goal is to facilitate border crossing, for others it is to gain public sympathy, or to expose that capital is free to circulate but people are not. Other activists have still other goals.
Many people talk about blocking traffic.
This would justify custom officers in denying entry to all activists on the ground that they are likely to do the same in Canada. Therefore, it is not clear how it would facilitate border crossing. Being prevented from reaching a goal is the definition of frustration. It is much better to let the custom officers themselves frustrate the population by denying them entry in Canada. They will be particularly tough at that period and they will probably stop lots of people who are not activists.