Been there, done that as a QA tester.

I ... Don't get it. Is this supposed to be funny?

For software/hardware designs of any substantial size, there's usually a separate (from the developer) person/team that does Quality Assurance (QA) testing & verification on a design. This has proven (over many decades) to be useful methodology to catch bugs because a developer has pre-conceived notions of how it should work and be used - so they don't think about edge cases. The QA person's job is to find a way to break it, so the final product has less bugs.

In the video above, the developer is on the left - you assumed she made the bucket lid and the pieces that go in the various holes. The QA person is on the right, demonstrating the problem(s) with the implementation. They get bonus points for making the dev's cry.

been on both sides
i think this would be more devs vs users. The testers would be trying to create their own holes or trying to push a dump truck through an existing hole